physics paper 1 Flashcards

Question 1

Q

What’s the difference between scalar and vector?

1 mark

Answer

A

Vector is magnitude and direction
Scalar just has magnitude

Question 2

Q

What are examples of scalar and vector

4 marks

Answer

A

vector:
- velocity
- displacement

scalar:
- distance
- speed

Question 3

Q

What is acceleration?

1 mark

Answer

A

The change in velocity over time.

Question 4

Q

What is uniform acceleration

2 marks

Answer

A

Acceleration due to gravity is uniform for the objects falling
use this equation in the exam (v^2 - u” = 2 x a x X(distance))

Question 5

Q

What are the units for these

Distance
Speed
Time
Velocity
Acceleration

make you you convert into these before calculating (5 marks)

Answer

A

metres
m/s
s
m/s
m/s^2

Question 6

Q

What does these things show in a distance/time graph

Gradient
Flat
Curve
Diagonal

4 marks

Answer

A

speed at that point (tangent)
stopped
acceleration
constant speed

Question 7

Q

What do these things show in a velocity/time graph

Gradient
A flat
Diagonal
Curve
Area under graph

5 marks

Answer

A

acceleration at that point (tangent)
constant speed
contant acceleration
Changing acceleration
The distance travelled

Question 8

Q

What is Newton’s first law

1 mark

Answer

A

If the resultant force on a stationary object is zero, the object will remain stationary if the resultant force of a moving object is zero, it will just carry on moving at the same velocity.

Question 9

Q

What are the units for these things

Force
Mass
gravitational feild strength
momentum

2 marks

Answer

A

Newtons
kg (but grams in chem)
N/kg
kg m/s

Question 10

Q

Why are large decelerations dangerous? what are the safety features to stop it?

3 marks

Answer

A

Can cause serious injury due to large force
Force can be lowered by slowing down the object over a longer period of time
Seat belt stretch. airbags slow down gradually. Crumple zones which crumple up easier, increasing the time to stop.

Question 11

Q

What does circular motion mean for the velocity, speed and acceleration?

Answer

A

speed is constant
velocity is constantly change
meaning its accelerating
this means there is a resultant force moving towards the centre of the circle

centripetal force

Question 12

Q

practical

How can you investigate the motion of a trolley on a ramp?

7 marks

Answer

A

Measure the mass of the trolley and the hanging hook. Then the length of the piece of card that will interrupt the light gate beams.
Adjust the height of the ramp into the trolley just starts to move
Mark a line on the ramp just before the first light gate for it to start each time
Attach the trolley to the hanging masses by the string and then let go.
Each light gate will record a time of the trolley passing and the speed of the trolley at that time.
acceleration = (speed at second light gate - speed at first light gate)/ time between the light gates
repeat with diffrent masses but the same everthing else

Question 13

Q

in the trolly experiment why do you change the height so it just starts moving?

1 mark

Answer

A

It means that the main cause of the trolley accelerating is due to the weight of the mass at the end.

Question 14

Q

How could you find someone’s walking speed

3 marks

Answer

A

Measure a distance with a tape measure
With a stopwatch time, how long it takes for them to get there
distance / time = speed

Question 15

Q

What is newton’s third law?

1 mark

Answer

A

When two objects interact, the forces they exert on each other are equal and opposite.

Question 16

Q

What is an object’s a inertial mass?

2 marks

Answer

A

How difficult it is to change the velocity of an object
force / accerleration = inertial mass

Question 17

Q

If two people with different masses pushed on each other who would accelerate more?

3 marks

Answer

A

Due to equal and opposite forces they will both exert the same force
due to force / mass = acceleration
the one with the lower mass will be accelerating more

Question 18

Q

What is a conservation of momentum

1 marks

Answer

A

Total momentum before is the same as the total momentum after.

Question 19

Q

What increases your stopping distance?

6 marks

Answer

A

thinking distance:
- reaction time - Increases with tiredness alcohol, drugs and distractions.
- speed - The faster you’re going the further you travel during your reaction time

breaking distance:
- speed - The faster a going, the longer it takes to stop
- mass - The more mass, the slower it will stop.
- condition of breaks - If the brakes are worn or falsely, it won’t go to break with as much force
- friction - The lower the friction, the slower it will take to stop

Question 20

Q

How do you use the ruler drop experiment to test reaction time?

7 marks

Answer

A

Get someone to hold a ruler so it hangs above your thumb and finger Lined up with zero
Without any warning, the person drops it and. you have to try and catch it as quick as possible by closing you thumb and finger together
Measure how far the ruler dropped in a time it took to react
Because acceleration is constant, you can use the equations To work out how long the ruler was falling for
2 x 10m/s^2(as acceleration is equal to gravity) x distance = change in velocity^2 then square root and divide by 10 (acceration again) to get the time
Make sure you do lots of repeats as it’s hard to do it accurately
Make sure everything is the same, like the ruler and the person dropping it.

Question 21

Q

What is the average reaction time of a driver and mass of car / bus / lorry

4 mark

Answer

A

1s
1000kg
10,000kg
30,000kg

Question 22

Q

A car is travelling at 25m/s and makes an emergency stop. The breaking force applied is 5000N estimate the total distance taken to stop.

5 marks

Answer

A

1/2 x m x v^2 = f x d (kenetic energy = work done)
rearange to get d = (1/2 x m x v^2) / F
d = (1/2 x 1000 x 25^2)/ 5000
d = 62.5
62.5 + (1x25) = 87.5m (adding on thinking distance)

Question 23

Q

What other 8 energy stores?

8 points

Answer

A

Kinetic
Thermal
Chemical
Gravitational potential
Elastic potential
Electrostatic
Magnetic
Nuclear

Question 24

Q

What are the four ways Energy can be transferred between stores.

4 points

Answer

A

Mechanically
Electrically
By heating
By radiation

Question 25

Q

What energy transfers are happening?

Hitting a ball with a bat
A car slowing (without breaking)
A kettle boiling water

3 marks

Answer

A

kinetic from bat mechanically goes to kinetic energy in the ball (and some to thermal mechanically and due to heating)
kinetic is transferred mechanically due to friction then by heating to thermal
Energy is transferred electrically from the main then Too thermal energy through heating.

Question 26

Q

How can you reduce energy transferred by friction?

4 marks

Answer

A

Lubrication
Whenever something moves, there is at least one friction force acting against it
This transfers energy mechanically to thermal energy store Which dissipates into surroundings by heating?
Lubricants can’t be used to reduce the friction. They include liquids like oil, which can easily flow between objects and coat them.

Question 27

Q

What reduces the rate of energy transfer by heating

5 marks

Answer

A

Insulation
In a building, the lower the thermal conductivity of the walls, the slower the rate of energy transfer though them.
Some houses have cavity walls made up of an inner and outer wall with a air gap in the middle, which reduces the amount of energy transferred by conduction.
Conduction is where hotter. particles vibrate and collide with each other, transferring energy from their kinetic store to other particles which make. them vibrate faster.
The thicker the wall, the slower the rate of energy transfer

Question 28

Q

What are the non-renewable energy resources?

5 marks

and what are the benifits/weakness

Answer

A

fossil fuels like coal oil and natural gas are reliable and have still enough to meet current demands.
Fossil fuels are cheap to extract and run
However, there are still slowly running out and cause environmental problems like global warming and the greenhouse effect and acid rain due to sulfur dioxide + oil spilages
Nuclear power is costly. to build and safely decommission
However, a nuclear power is clean and Will last much longer than fossil fuels but nuclear waste is very dangerous and difficult to dispose of

Question 29

Q

What are the renewable energy resources?

6 marks

Answer

A

Biofuels
Wind
solar
hydro-electric
tides
These will never run out and dont damage the environment. However, the problem is they are unreliable and dependent on the weather.

Question 30

Q

what are bio-fuels?

Answer

A

renewable energy made by plants or animal dung
carbon neutral (if you grow at the same rate you burn
fairly reliable as crops dont take too long to grow and it can be done all year round
can be stored for an immediate energy demand
cost is high and use neutrients which would be used for crops made for food
forests are sometimes cleared which destroy habitats

Question 31

Q

What is wind power?

5 marks

Answer

A

Turbines have generators inside - when wind rotates the blades They turn a generator producing electricity with no pollution.
Initial costs are high, but running costs are low
Lots of them are needed to produce much power as fossil fuels
Some people think they spoil the view and can be noisy and annoying.
They only work when it’s windy, so you can’t always supply electricity or respond to high demand.

Question 32

Q

What are solar cells

6 marks

Answer

A

solar cells use energy transferred by light to create an electric current
Solar power is often used in remote places where power can’t normally get to.
There’s no pollution
Initial costs are high but there’s no running cost
They mainly are used to generate electricity on a relatively small scale (a home)
Solar power is most suitable for sunny countries but can be used in cloudy countries As you can’t make solar power at night or increase production when there is extra demand

Question 33

Q

What is hydroelectricity

5 marks

Answer

A

Producing hydroelectricity usually involves flooding a valley by building a big dam
Rainwater is caught and allowed out through turbines making electricity with no pollution
There is a big impact on the environment due to the flooding of the valley and possible loss of habitat
A big advantage is that it can immediately respond to an increase in demand as more water can be let through the turbines to generate more electricity
Initial costs are often high but there is minimum running cost and it’s very reliable

Question 34

Q

What are tidal barrages?

4 marks

Answer

A

They are big dams built across rivers with turbines in them as the tide comes in it fills the estuaries and the water is then let out through turbines at a controlled speed to generate electricity
There is no pollution but they affect boat access and spoil the view and the alter the habitat for wild life
Tides are pretty reliable but the height of the tide is variable and the barrages don’t work when the water is the same level both sides
Initial costs are moderately high but there are no fuel costs and minimal running costs

Question 35

Q

How are we trying to change our energy usage

8 marks

Answer

A

Electricity in the uk hugely increased as the population got bigger
As appliances get more efficient the usage of energy slowly decreases
Some of our energy is being produced using fossil fuels and nuclear power but the rest is renewable energies
We use a lot of fossil fuels for cars and gas heating
Renewable energies can be used for those purposes as well like solar water heaters to heat buildings
We are trying to increase our renewable energy resources
Pressure from other countries and the public means that the government have introduced targets for renewable energy resources putting pressure on energy providers so they don’t lose their business
hybrid and electric cars

Question 36

Q

How is the use of renewables limited by the reliability and money and other issues?

6 marks

Answer

A

Building new renewable power plants cost money and smaller energy providers are reluctant in doing this as fossil fuels are much more cost effective
There are arguments where new power plants should go as people don’t want to live next to wind farms and it could lead to protests
Some energy resources like wind arent as reliable due to them not being able to increase the power output on demand
This means that they would have to use a combination of different power plants
Research into improving reliability and cost of renewable energy resources takes time and money even with funding it might be years before an improvement is made
Making personal changes might also be quite expensive as hybrid and electric cars are more expensive and things like solar panels are still quite pricey

Question 37

Q

What are these parts of waves

Amplitude
Wavelength
Trough
Crest
Frequency
period
Rest position

7 points

Answer

A

The displacement from the rest position to a crest or trough
The length of a full cycle of a wave
The lowest part of the wave
The highest part of the
Number of complete cycles per second
The number of seconds it takes to do one cycle
The middle line of a wave

page 32

Question 38

Q

What is the difference between transverse weave and a longitudinal wave

6 marks

Answer

A

** Transverse:**
- all Electromagnetic waves
- Vibrations are perpendicular to the direction the wave travels
- S-waves
- ripples and waves in the water

** Longitudinal:**
- Vibrations are parallel to the direction of the wave
- P-waves
- They squash up and scretch out in areas of compression(high pressure) and rarefactions(low pressure)

Question 39

Q

How do you use an Oscilloscope to measure the speed of sound?

5 marks

Answer

A

Attach a signal generator to a speaker so you can generate a sound with a specifc fequency
Set up an oscilloscope so the detect waves at each microphone show up as separate waves
Start with both microphones next to the speaker then slowly move one away until the two waves are aligned on the display but have move exactly one wave length apart
Measure the distance between the microphones to find one wavelength
do frequency (is what the signal genorator is set to) x wavelength to find the speed

page 33

Question 40

Q

how can you measure the speed of water ripples using a strobe light?

6 marks

Answer

A

Using a signal generator attach the dripper of the Ripple tank to create water waves at a set frequency
dim the lights and turn on the strobe light to see wave patterns made from shadows of wave crests
alter the frequency of strobe light until the pattern freezes
this means the frequency of wave and light are equal because the wave will be lit at the same point in their cycle each time
the distance between each shadow line is equal to one wave length - the the most accurate value measure 10 wave lengths and find the average
do frequency ( set by signal generator) x wavelength to get the speed

Question 41

Q

How can you use peak frequency to find the speed of a wave in a solid?

6 marks

Answer

A

Set up an experiment where an rod secured in the cente and held up by elastic bands
Measure and record the length of the metal rod
Get a microphone connected to a computer at one end of the rod and get a hammer on the other
Tap the rot with the hammer and write down the peak frequency displayed by the computer
Repeat this three times and get an average peak frequency
Calculate the speed of this wave by doing frequency x wavelength (which is 2x the length of the rod)

Question 42

Q

What are three things that can happen when I wave meets a boundary?

3 marks

detail

Answer

A

It can be absorbed by the second material - wave transfers energy to the material often thermal store leading to heating
It can be transmitted - The wave carries on travelling through the new material often refracting
It can be reflected - This is where the weave is sent back in the direction it came from causing echos

Question 43

Q

How would you draw a ray diagram?

5 marks

Answer

A

Draw the boundary between two materials and a normal which is 90 degrees to the boundary
Draw the incident ray that meets the normal at the boundary
the angle between the Ray and the normal is the angle of incidence
Now draw the refracted array on the other side of the boundary(If the second material is more dense the ray bends towards the normal otherwise it bends away
The angle between the refracted ray and the normal is the angle of refraction

Question 44

Q

what determines which fequency an object can transmit?

3 marks

Answer

A

size
shape
structure

Question 45

Q

what happends when a sound wave hit a solid?

2 marks

Answer

A

particals in solid move back and forth
they hit the next particle in the line ect.

Question 46

Q

how do you hear?

6 marks

Answer

A

sound wave gets to your ear causing it to vibrate
these vibrations pass on to tiny bones in your ear called ossicles though the semicircular canal nd to the cochlea
which turns vibrations into electrical signalswhich get sent t your brain
the brain interprets the signals as sounds of diffrent pitches and volumes
which depend on the frequency and intensity (higher frequency - higher pitch
human hearing is limited to the size and shape of the eardrum and the structure of the diffrent parts that vibrate

Question 47

Q

what is ultrasound?

4 marks

and how is it used

Answer

A

sound at 20,000Hz
when a wave passes from 1 medium to another some is reflected (partial reflection)
this means you can point a pulse of ultrasound at an object and get some ultra sound back
the time/2 of how long it takes to send the pulse and detect it - is how far away it is

Question 48

Q

how is ultrasound useful in medical imaging and industrial imaging?

6 marks

Answer

A

medical imaging:
1. ultrasound waves can pass though the body but when they reach a boundary some of the wave is reflected back and detected
2. timings and distribution of echos a processed by a computer to produces a video
3. it is complete safe

industry:
- ultrasound can be used to find flaws in pipes and maturials
- ultrasound waves entering a maturial will usually be reflected by the far side
- if there is a flaw (like a crack) the wave will be reflected sooner

Question 49

Q

what is infra sound

3 marks

Answer

A

Sound with frequencies lower than 20Hz
how some animals communicate
can be produced by natural events (e.g. earthquakes)

Question 50

Q

what waves do earthquakes produce?

4 marks

how are they useful

Answer

A

seismic waves (P-wave/S-waves)
they refract out boundarys and curve the path
by observing how they are absorbed and refracted scientists were able to work out where properties of the earth changed
this increase our understanding of the internal structure of the size of earths core

Question 51

Q

what are the diffrences between p-waves and s-waves

5 marks

Answer

A

P-waves:
- longitudinal
- passes though solids and liquids
- faster then s-waves

S-waves:
- transverse
- only go though solids
- slower then P-waves

page 37

Question 52

Q

how do you draw a ray diagram for reflection?

5 marks

Answer

A

angle of incidence = angle of relection
normal = perpendicular to the boundary
angle of incidence = incident ray to normal
angle of refection = normal to reflected ray
normal is shown as a dotted line

Question 53

Q

what is total internal reflection?

6 marks

Answer

A

wave is reflected back into material
only when wave travels from a more dense towards a less dense material
happens when the angle of incidents (i) is larger then the critical angle
every boundary has its own critical angle
when i is less the critical = most is refracted - some is internaly reflected
when i equals critical = most of the ray goes along surface
when i > critical = no ligh comes out more dense area (total internal reflection

page 38

Question 54

Q

what is specular / diffuse reflection?

4 marks

Answer

A

specular reflection = waves are reflected in a single direction by a smooth surface
this means you get a clear refection (mirror)
diffuse refection = refected on a rough surface and the waves are reflected in all directions
because the normal is diffrent for each ray

page 38

Question 55

Q

Practical

How would you investigate refraction using a glass block?

7 marks

Answer

A

Place a rectangular glass block on a piece of paper and trace around it
use a ray box to shine a ray of light at the middle of the block at an angle
Trace the incident Ray and the emergent Ray on the other side of the block. then remove it and join up the lines To show the path of the refracted ray
Draw the normal at a point where the ray enters the block and use a protractor to measure the angle of incidence (between incident ray and normal) and angle of refraction (between refracted ray and normal)
Do the same for where the point emerges from the block
Repeat this three times keeping the angle of incidence the same
Calculate the average for these angles

Make sure you’re in a dim room so you can clearly see the ray
The Ray light must be thin so you can easily trace the middle
To do this cut a thin slit in a light box allowing a thin ray of light out

Question 56

Q

What should you see from a refraction practical?

3 marks

Answer

A

you should see that the light bends towards the normal as it enters the block
This is because the block will have a higher density
You should then see the ray of light move away from the normal when it leaves the block

All electromagnetic waves retract

Question 57

Q

How does colour and transparency depend on absorbed wavelengths?

7 marks

Answer

A

Different objects absorb transmit and reflect different wavelengths
Opaque objects do not transmit light
The colour of an object depends on which wavelength of light are reflected
Colours can also mix so a yellow object might look yellow because it is either reflecting yellow or both red and green light
White objects reflect all wavelengths of visible light equally
Black objects absolve all wavelengths
Transparent and translucent objects transmit light Passing through

Question 58

Q

How do colour filters work?

4 marks

Answer

A

They only let certain colours (wavelengths) transmit and the rest are absorbed
If you put a blue collar philtre in front a white object it will look blue because it only lets the blue wavelength pass through
If a blue filter was put in front of a red object it will appear black because all of the light will be absorbed
Primary colour filters only let through that particular light But none primary colour filters will let through both the wavelengths of light corresponding to that colour

Question 59

Q

What are the difference between the lenses?

6 marks

Answer

A

Converging (convex):
- Thicker middle
- causes parallel rays to come together
- The principal focus is where All the parallel lines meet

diverging (concave):
- caves in words
- Causes parallel rays to spread out
- The principal focus is where the Rays hitting the lens appears to come from if you trace back and till they meet up

Question 60

Q

What’s the difference between a real and virtual image?

2 marks

Answer

A

real - It’s formed when light rays actually come together to form an image and it can be captured on a screen
virtual - Is when the light rays from the object appear to be coming from a completely different place to where they actually came from and they don’t actually come together

Question 61

Q

What does power have to do with lens curvature

5 marks

Answer

A

The more powerful the lens the more strongly it converges (brings together) rays of light so the shorter the focal length
in Converging lenses the power is positive and In diverging lenses the power is negative
To make a more powerful lens we would need to have a stronger curved surface
Some materials are better at focusing light than others meaning a powerful lens can be made thinner by changing the material
Using a material that is better at focusing light means you don’t have to make the lens as curved to get the same focal length

Question 62

Q

How do you produce a ray diagram for an image through a diverging lens?

6 marks

Answer

A

Go from the top of the object and draw a parallel line to the axis of the lens
Draw another ray from the top of the object going right through the middle of the lens
From the principal focus on the left side draw a The dotted line (angle of i) to Where the hight of the object and the lens meet
Mark where the angle of incidence and the line from the object through the middle, meet
This is the top of the virtual image
The image is always virtual, the right way up, smaller and on the same side

page 42

Question 63

Q

How do you draw a ray diagram for an image through a converging lens?

4 marks

Answer

A

Draw a parallel line from the top of the object to the lens
Draw another ray going from the top of the object to though the middle of the lens
The incident ray goes from where the parallel line meets the lens through the focusing point on the right
Where the incident ray and the line that goes through the middle meet is where the image forms

Question 64

Q

How does the distance between the lens and the object affect the size and position of the image in a converging rad diagram?

4 marks

Answer

A

more the 2F = real, inverted and smaller
2F = real, inverted and same size
F=< O < 2F = real, inverted and bigger
less then F = virtual, upright, bigger and on the same side

Answer 65

A

Transverse waves
They all travel at the same speed for a vacuum but different speeds in different materials
They are between 10^-5 and 10^4 metres
They are generated by A variety of changes in atoms and their nuclei giving a range of frequencies
They transfer energy from a source to an absorber
The higher the frequency the more energy it transfers

Answer 66

A

radio waves - Transmitted through the body without being absorbed
Microwaves - Can be absorbed causing heating of cells
Infrared - Mostly reflected or absorbed by the skin causing some heating And can cause burns
Visible light - Mostly reflected or absorbed by the skin causing some heating
Ultraviolet - Is absorbed but has a higher frequency so more dangerous. it’s a type of ionising radiation and can damaged cells possibly leading to skin cancer or eye conditions
X-rays/gamma - ionising and can cause mutations and damage cells And get deeper into tissues

Answer 67

A

The higher the intensity of the wavelength the higher the temperature
If the average power that the object absorbs is more than average power it radiates the object heats up vise versa
An object at a constant temperature radius and absorbs the same average power

Answer 68

A

The overall temperature depends on the amount of radiation that is reflected, absorbed and emitted
Radiation is reflected and absorbed by Earths atmosphere clouds and surface
During the day lots of radiation is transferred from the sun (increaing temp) but at night radiation is emitted by the atmosphere causing a decrease in the local temperature

Answer 69

A

Wrap 4 identical test tubes with material that is the same but different colours
Boil water in a kettle and fill each test tube with the same volume of water
Use a thermometer to measure the temperature of the water every minute
Seal the test tubes with bungs between the measurements
The temperature will decrease quicker in test tubes surrounded by surfaces that are good emitters of radiation

Answer 70

A

Alternating currents made up of oscillating charges can produce Oscillating electric and magnetic feilds (what EM waves are made from)
You can produce radio waves by using an alternating current in an electric circuit
The object which charges oscillate to create radio waves is called a transmitter
Transmitted radio waves Ritchie receiver where the radio waves are absorbed
The energy carried by the waves is transferred to the electrons in the material of the receiver
This energy causes electrons to oscillate and if it’s part of a complete circuit it will generate a alternating current
This current will have the same frequency as the radio wave

Answer 71

A

Longwave radio can be received halfway around the world because they can bend around the curved surface of the Earth Allowing the signal to be received even if it isn’t in line of sight of the transmitter
Short-wave radio signals Can be received at long distances because they are reflected by the Earth’s atmosphere
This allows radio waves to be great for communication and broadcasting
Bluetooth uses shortwave signals to send data over a short distances without wires
Radio waves for TV and radio stations Have very short wavelengths as you must be in direct sight of the transmitter to get reception

Answer 72

A

Communication to and from satellites use EM waves which can pass easily through Earths atmosphere
These can usually be microwaves but sometimes high frequency radio waves
For satellite TV the signal from a transmitter is transmitted into space and received by a receiver dish orbiting above Earth
The satellite transmits the signal back to Earth in a different direction, where it’s received by a satellite dish on the ground

Answer 73

A

The microwaves are absorbed by the water molecules in the food
Microwaves penetrate through a few centimetres into the food before being absorbed and transfering the energy they are carrying to the water molecules in the food causing the water to heat up
The water molecules then transfer this energy to the rest of the molecules in the food by heating which quickly cooks the food

Answer 74

A

Infrared radiation is given out by all hot objects
Infrared cameras can be used to detect infrared radiation and monitor temperature
The camera detects the infrared radiation and turns it into an electrical signal which is displayed on a screen (thermal imaging)
Thermal imaging is used by the police to see its suspects that are trying to escape or hide in the dark
Infrared sensors can be used in security systems to detect a change in infrared radiation, causing an alarmed go off or a security light to turn on
absorbing infrared radiation causes objects to get hotter so food can be cooked using infrared radiation as the temperature of the food increases when it absorbs it
Electric heaters use infrared radiation as they contain a long piece of wire that heats up when a current flows through it. This wire then admits lots of infrared radiation which is absorbed by objects and the air so the energy is transferred into a thermal store increasing the temperature

Answer 75

A

It can be used to send files between devices
TV remotes use it
Optical fibres are thin glass or plastic fibres that carry data over long distances as pulses of infrared radiation. They usually use a single wavelength to prevent desperation which could lose some information
They use total internal reflection to send lots of data over a long distance

Answer 76

A

Illuminating things
Photographic film reacts to light to form an image -> This is how traditional cameras create photos
Digital cameras contain image sensors which detect visible light and generate an electrical signal which is converted into an image that can be stored

Answer 77

A

Fluorescence is a chemical where ultraviolet radiation is absorbed and visible light is emitted
They use ultraviolet to admit visible light and are energy efficient so they are good when light is needed for long periods.
Security pens can be used to mark property and only can be seen under ultraviolet light as it will glow up the ink
bank notes and parasports use a similar technique to detect forgeries
It can also be used to sterilise water as it kills bacteria making it safe to drink

Answer 78

A

They affect photographic film the same way like it does meaning you can take X ray photographs (now they are produced electronically)
Radiographers In hospitals take X-ray images to help doctors diagnose broken bones as X-rays are transmitted by flesh but absorbed by denser materials like bones
To produce an image, X-ray radiation is directed through the object or body into a detector plate, the brighter bits of the image are where fewer X rays get through producing a negative image
X rays are also used in airport security scanners to detect hidden objects that can’t be detected with metal detectors

Answer 79

A

Cameras are used to sterilise medical instruments as they kill microbes
Food can be sterilised in the same way as it keeps food fresh for longer without having to freeze it, cook or preserve it and it’s perfectly safe to eat
Some medical imaging techniques such as traces use gamma rays to detect cancer
Gamma radiation is also used in cancer treatments as it targets the cancer cells to kill them, Doctors have to be careful to minimise the damage to healthy cells when treating cancer like this

Answer 80

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In 1897 JJ Thompson discovered that electrons could be removed from atoms so atoms must be made of smaller bits
He suggested the plum pudding model where atoms had a face of positive charge with tiny negative electrons in them
In 1909 Rashford tried firing a beam of alpha particles at a thin gold foil They expected all the particles to pass through however some were deflected back
this meant all the Mass was concentrated in the centre (Nucleus)
He realised most of Atom was mostly empty space with a charged nucleus and tiny electrons around it (The nuclear model)
Bohr tweaked this idea where electrons were in fixed orbits and at set distances called energy levels - he suggested that electrons can only exist in these shells and nowhere in between

Answer 81

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Electrons sit in shells where each energy level is a different distance from nucleus
An inner electron can move up to a higher energy level if it absorbs electromagnetic radiation with the right amount of energy
If it does move up a shell it is said to be excited
The electron will quickly fall back into its original energy level and in doing so it will omit the seamount of energy it absorbed
The part of the en spectrum that is admitted from the atom depends on its energy - Higher energy higher frequency
As you move further out from the nucleus the energy level will get closer (smaller diffrents in amount of energy
This means that the further away you are from the nucleus the at less energy will be edmitted

Answer 82

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Radiation that can knock off electrons form an atom Causing it to become ionised

Answer 83

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Isotapes of an element that tend to decay into other elements and give out radiation as they try to become more stable ( They go through radioactive decay )
Radioactive substances spit out one or more types of ironizing radiation when they decay

Answer 84

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Alpha radiation is when an alpha particle is admitted from the nucleus
An alpha particle is two neutrons and two protons ( Helium nucleus )
They don’t penetrate very far into materials and are quickly stopped by only a few centimetres in the air and is absorbed by a thin sheet of paper
Due to their size they are strongly ionising

Answer 85

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Beta minus is a fast moving electron released by the nucleus
They have virtually no mass and a relative charge of -1
they have a range of a few metres and are absorbed by a sheet of aluminium
Beta plus particles is a fast moving positron an antiparticle of an electron
It has the same mass but +1 charge
They have a smaller range because when they hit an electron they destroy each other and produce gamma rays
They both are moderately ionising

Answer 86

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After a nucleus has decayed it goes under nuclear rearrangement which releases energy
Gamma rays or waves of EM radiation released by the nucleus that carry this energy
They penetrate far into materials without being stopped and travel long distances through the air
This means they are weakly ironizing because they tend to pass through rather than collide with atoms - Eventually they hit something and do damage
They can be absorbed by thick sheets of lead or metres of concrete

Answer 87

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The mass number decreases by 4
the atomic number decreases by two
And it emits a alpha particle

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Answer 88

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It loses and neutron but gains a proton so the mass stays the same
the atomic number increases by one as there is one more proton
A beta minus particle is emitted

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Answer 89

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It loses a proton but gains a neutron so the mass doesn’t change
The atomic number decreases by one as it lost a proton
A positron is emitted

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Answer 90

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The mass number of decreases by one as it lost a neutron
The atomic number stays the same
A neutron is emitted

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Answer 91

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Radioactive sources contain radioactive isotopes that give out radiation
Decaying nuclei is a random process
The rate which a source decays is called activity and it’s measured in Becuerels (Bq)
1Bq = One decay per second
It can be measured using a Geiger Miller tube which clicks every time it decays radiation
It can be attached to a counter which displays the number of clicks per second
You can detect radiation using a photographic film - The more radiation is exposed to the darker it becomes

Answer 92

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The average time taken for the number of radioactive nuclei in an isotope to half
The activity never reaches zero
short half-life mean the activity falls quickly because the nuclei is very unstable and rapidly decays Meaning is very dangerous because of the high amount of radiation they edmit but they become safe more quickly
A long half-life means the activity falls more slowly because mostly nuclei doesn’t decay for a long time - the source just sits there releasing a small amount of radiation. It is dangerous because nearby areas are exposed to radiation for many years

Answer 93

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It naturally occurs in unstable isotopes which are all around us (The air, some foods, buildings and rocks)
It comes from space known as cosmic rays which are mostly from the sun but luckily the Earth’s atmosphere protects us from it
Human activity like nuclear explosions or nuclear waste but this represents a tiny proportion

Answer 94

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Irradiation
Objects near a radioactive source are irradiated by it
This does not make it radioactive
Keeping sources in lead lined boxes standing behind barriers or being in a different room our ways of reducing the effect of a radiation - Medical staff who work with radiation also were photographic film badges to monitor their exposure

Answer 95

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If unwanted radioactive atoms get onto an object it becomes contaminated
These contaminating atoms might then decay releasing radiation which could cause harm
this is very dangerous as it may get inside your body
Once someone has been contaminated they are at risk until the contamination is removed or the reactive atoms have decayed
Gloves and tongues should be in use when handling sources to avoid parties getting stuck in your skin - some workers were protective suits to stop them breathing in particles

Answer 96

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It can enter living cells and ionise atoms and molecules within them leading to tissue damage
Lower dosage tend to cause minor damage without killing the cell but can give a rise to mutant cells which divide uncontrollably (cancer)
Higher dosages tend to kill cells completely causing radiation sickness if a lot of cells all get blattered at once
Outside the body beta and gamma radiation is the most dangerous because they can penetrate the body and get to the organs where Alpha can’t get through
Inside the body alpha sources are the most dangerous as they’re strongly ionising so they can damage in a very localised area meaning it can contaminate

Answer 97

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the lowest activity of a radioactive source the safer it is to be around
if two sources have the same amount of activity the one with the longer half life will be more dangerous
If the initial activity is lower for the longer half life, it will become more dangerous after a certain period as the activity will fall more slowly
You need to find the right balance between the right level of activity that isn’t too dangerous for too long
You also need to be careful planning storage and disposal especially with sources with long half life

Answer 98

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A weak source of alpha radiation is placed in a smoke detector close to two electrodes
The source causes ionisation and a current of charged particals to flow
If there is a fire then smoke will be absorbed by the charged particles using the current to stop sounding an alarm

Answer 99

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Food can be eradicated with high dosages of gamma rays which kill all microbes meaning they dont go as bad as quickly
Medical equipment can be sterilised using gamma rays instead of being boiled
irradiation is a particularly good method to sterilise because unlike boiling it doesn’t involve high temperatures so things can be sterilised without being damaged
The radioactive source used for this need to be very strong emitter of gamma rays with a reasonably long half life so it don’t have to be replaced too often

Answer 100

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A medical tracer is injected into a patient and is moved around the body followed by an external detector this method can be used to detect and diagnose medical conditions e.g. cancer
All isotopes which are taken into the body must be beta or gamma emitters so radiation can pass out of the body without doing too much damage - They should only last a few hours so the radioactivity inside the patient quickly disappears

Answer 101

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Gamma emitting traces are also used in industry to detect leaks in underground pipes
Beta radiation issues in thickness control
This is done by directing radiation through stuff being made (e.g. paper) and putting a detector on the other side and connecting it to a control unit
When the amount of detected radiation changes it means the paper coming out is too thick or too thin so the control unit adjusts the roller to give the correct thickness
It needs to be a beta source because then the paper will partially block the radiation

Answer 102

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positron emission tomography is a technique to show tissue or organ function and can be used to diagnose medical condition
The patient is injected with a substance used by the body contending a positron emitting radioactive isotope with a short half-life acting as a tracer
Positron’s Emitted by the isotope meat electrons in the organ and annihilate emitting high energy gamma rays in opposite direction that are detected by detectors around the body - By looking where all the rays meet the tumour can be accurately found
The distribution of radioactivity matches up with the metabolic activity because more of the radioactive thing that was injected is taken up by the cells that are doing work
the isotope used in PET scanning have short half life so it’s important they are made close to wherever they’re going to be used
Otherwise if it had to be transported over a large difference the activity will be too low the time it arrived at the hospital

Answer 103

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internal:
- With internal radiation therapy A radioactive material is placed inside the body into or near a tumour through injecting or implanting a small amount of radioactive substance
- Alpha emitters are usually injected into the tumour as its strongly ionising and can do a lot of damage put the damage to normal tissue surrounding the tumour is limited because they have such a short range
- Beta emitters are often implanted into the tumour before damaging nearby cancerous cells, as they have longer ranges they can damage healthy cells further away
- The half life of the source used for internal treatment is usually short to limit the time that radioactive substances are inside the patient’s body

external:
- tumours can be treated externally using gamma rays aimed at the tumour - The radiation is carefully focused on the tumour and sometimes shielding is placed on other areas of the body but some damage can still be done to surrounding healthy cells
- The sources in external radiotherapy treatments should have long half lifes so they don’t have to be replaced often
- The machines used for radiotherapy are often surrounded by feuding and captain-designated rooms to reduce the risk of staff and patience

Answer 104

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A slow moving neutron is fired at a large unstable nucleus - often uranium 235 - the neutron is absorbed by the nucleus making it more unstable causing it to split
When uranium two three five splits it forms two new lighter elements and energy is released
There are lots of different pairs of atoms that uranium can split into but these new nuclei are radioactive
Each time uranium atom splits it also splits out two or three neutrons that can hit other uranium nuclei causing them to split causing a chain reaction

Answer 105

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Neutrons released by fission have lots of energy
These neutrons will only cause other nuclear fission if they are moving slowly enough to be captured by uranium nuclei in the control rods - These slow moving neutrons are called thermal neutrons
To do this the uranium fuel rods are placed in a moderator to slow down the fast moving neutrons
Control rods are often made of boron to limit the rate of fission by absorbing the access neutrons they are placed but in between the few rods and are raised and lowered into the reactor to control the chain reaction
This creates a steady rate nuclear fission where one new neutron produces another fission
If this chain reaction in a nuclear reactor is left to continue unchecked large amounts of energy are released in a very short time causing a runaway reaction which could lead to an explosion

Answer 106

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Energy released by fission is transferred into the thermal energy store of a moderator
This is then transferred to the thermal energy store of the coolant and then the thermal energy store of the cold water passing through the boiler
This causes the water to boil and to the energy to be transferred to the kinetic energy store of the steam
This energy is then transferred to the kinetic energy store of the turbines and then kinetic energy store of the generator
Energy is then transferred away from the generator electrically

page 57 for pic

Answer 107

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Two light nuclei collide at high speeds to join to create a larger heavier nucleus e.g. Hydrogen nuclei confuse to produce a helium nucleus
This heavier nucleus does not have as much mass as two separate light nuclei did
Some of the mass of the lighter nuclei is converted into energy and released

Answer 108

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Fusion has to happen at a very high pressure and 10 million degrees Celsius
Because the positively charged nuclei have to get very close to fuse so the strong forces due to electrostatic repulsion has to be overcome
It’s really hard to create the right conditions for fusion as no material can withstand that kind of temperature as it would vaporise so they’re hard to make and expenses to try and build
There have been a few experiments but it takes more power than is generated to get the temperature

Answer 109

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-
- People view it as very negative as they think it’s very dangerous
- Some people worry that nuclear waste can never be disposed safely as they have long half lives meaning they’ll be radioactive for hundreds/thousands/millions of years
- There is always a danger that it could leak out and pollute the land, rivers and oceans
- Nuclear power also carries the risk of leaks directly from the power station or a major catastrophic like Chernobyl
- The overall cost is high due to the initial cost of the power plant and dismantling the nuclear power plant safely takes decades

+
- Generally they are pretty safe at generating electricity and not as risky as some may think
- it is very reliable as it reduces the need for fossil fuels
- It does not contribute to global warming so it’s much better than fossil fuels
- Huge amounts of energy can be generated with a relatively small amount of nuclear material

Answer 110

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Asteroids are lump of rock and metal that orbit the sun, usually found in the asteroid belt
Comets are a lump of ice and dust that orbit the sun and are highly elliptical. some travel near to the sun to the outskirts of our solar your system

Answer 111

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Planets move around the sun in almost circular orbits meaning that it orbits at a constant speed and is constantly accelerating
The force causing this is the centripetal force
This force would cause the object to just fall towards whatever its orbiting but the object is already moving so it just causes it to change direction
The object keeps accelerating towards what is orbiting but the instantaneous velocity (which is at a right angle to the acceleration) keeps travelling in a circle
The force that makes this happen is provided by the gravitational force between the planet and the sun

Answer 112

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Gravitational field strength depends on the mass
Gravitational filled strength also varied with distance, the closer you are the stronger the force
The stronger the force the larger the instantaneous velocity needed to balance it
So the closer to a star the planet is the faster it has to move to remain in order
For an object in a stable orbit if the speed of the object changes the size of its orbit must do so as well

Answer 113

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Geocentric model was the first by the ancient greeks - it stated that everything orbited the Earth in perfect circles
This was because they didn’t have telescopes and saw the sun and moon travelling across the sky in the same way every day and light
The next was the heliocentric model - it said that the earth and all the other planets orbited the sun in perfect circles
Galileo found the best piece of evidence for this theory as the moons around Jupiter while looking for a telescope He noticed that some stars were in line near the planet But they never moved away showing not everything was orbiting around the Earth
As more technological advancements the evidence for this model increased
The current model still says planets orbit the sun but in an elliptical orbit rather than circular

Answer 114

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The universe has always existed and always exists
As the universe expands new matter is constantly being created
Density stays the same
This new beginning or no end
Supported by red shift

Answer 115

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What was the matter of the universe occupied a very small space
This tiny space was very dense and very hot
Then excluded and space started expanding
This theory gives a finite age for the universe
It’s supported by cosmic microwave background radiation and red shift

Answer 116

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Different elements absorb different frequencies of light
Each element produces a Spacific pattern of dark lines at the frequencies that it absorbs in the visible part of the EM spectrum
When we look at light from distant galaxies we see the same patterns but slightly lower frequencies
There’s an observed increase in wavelength of light coming from the galaxies and a pattern has been shifted towards the red end of the spectrum (red-shift)
Measurements of the redshifts suggest all the distant galaxies are moving away from us very quickly from all directions
More distant galaxies have a greater red shift meaning they have they are moving away faster providing evidence that the whole universe is expanding

This can have the same effect as the sound from a racing car

The noise sounds lower pitch when it’s travelling away from you because it drops in frequency (doppler effect)

Answer 117

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Scientists have detected low frequency electromagnetic radiation coming from all parts of the universe
This radiation is mainly the microwave part of the EM spectrum

Answer 118

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It initially starts from a cloud of dust and gas called a nebula
The force of gravity pours the dust and gas together to form a protostar
The temperature rises as the star gets denser and more particles collide
When the temperature gets high enough hydrogen nuclei undergo nuclear fusion to form helium nuclei giving out a huge amount of energy keeping the core hot
A star is born and enters a long stable period
During this time the outward pressure caused by thermal expansion balances the force of gravity pulling everything inwards (the heavier the star the shorter is time on the main sequence)

Answer 119

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Eventually the hydrogen in the core begins to run out and the force due to gravity is larger than the pressure of thermal expansion
The store is compressed into its dense and hot enough that hydrogen in its outer layer and helium in its core can undergo fusion
This increases the pressure of thermal expansion again making the outdoor layer of the star expand becoming a red giant or a red supergiant if it’s a super large star (red due to the cool surface)
A small star becomes unstable and ejects its outer layer of dust and gas leaving behind a hot dense solid core Which is a white dwarf

Answer 120

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They start to glow brightly again as they undergo more fusion to make heavier elements
They expand and contract several times as the balance shifts between gravity and thermal expansion
Eventually they explode in a supernova
the exploding supernova throws the outer layer of dust and gas into space leaving a very dense core called a neutron start
If the star is massive enough it will collapse and become a black hole

Answer 121

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They use refraction and reflection to allow you to see the distant objects
Optical telescopes are the ones that detect visible light
You can improve the quality by increasing the aperture of the telescope which is the diameter of the objective lens
Use a higher quality objective lens

Answer 122

A

The atmosphere absorbs a lot of light coming from space before it reaches us so to observe the frequencies which are absorbed, you have to be above the atmosphere
Light pollution makes it harder to pick out dim objects and reflects and absorbs light coming from space

To get your best view on Earth you should be on the top of a mountain in a dark place

Answer 123

A

Optical telescopes are used to look at objects close by and in other galaxies but many objects in the universe aren’t detectable using visible light
The telescopes developed for all parts of the EM spectrum allow us to see parts of the universe that we couldn’t see before like its structure
X-ray telescopes are a good way to see high temperature events in space like exploding stars
Radio telescopes are responsible for the discovery of cosmic back microwave background radiation helping scientists learn more about the origins of the universe
Bigger telescopes give us a better resolution and can give them more light so we can see things which we couldn’t see before it will server improved magnification so we can look further into space and discover new galaxies
Modern telescopes work alongside computers to help create clearer and sharper images

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