Physics Flashcards
How many energy stores are there?
8
Name all 8 energy stores
Kinetic, thermal, gravitational potential energy, elastic potential energy, electrostatic, magnetic, chemical and nuclear
What is the kinetic energy equation?
Kinetic Energy = 1/2 x Mass x Velocity^2
How is KE transferred to an object?
When the object speeds up
How is KE transferred from an object?
When the object slows down
What are two factors that affects the KE of an object?
It’s mass and it’s velocity
What would happen to the KE of an object if you were to double it’s speed?
The speed would increase by a factor of 4
What is the gravitational potential equation?
Gravitational Potential = Mass x Gravity x Height
Define conservation of energy
Energy an be stored, transferred between stores and dissipated - but it can never be created or destroyed. Therefore, the total energy of a closed system has no net change
What are the four ways energy can be transferred?
Radiation, heating, electrically and mechanically
Define energy transfer by radiation?
Energy transferred by waves
Define energy transfer by heating?
Energy transferred from a hotter object to a colder object
Define energy transfer by electrically?
A charge doing work
Define energy transfer by mechanically?
A force acting on an object
Give an example of energy transfer by radiation
Energy from the Sun reaching Earth by light
Give an example of energy transfer by heating
Heating a pan on a hob
Give an example of energy transfer electrically
Charges moving around a circuit
Give an example of energy transfer mechanically
Pushing, stretching or squashing an object
Define useful energy
Energy transferred from a store to a useful store
What is the efficiency equation?
Efficiency = Useful Energy / Total Energy
What are methods of reducing wasted energy?
Lubrication or thermal insulation
How does lubrication reduce wasted energy?
By reducing friction
What type of energy transfer is friction?
Mechanical (Kinetic -> Thermal)
How does insulation reduce wasted energy?
By reducing release of thermal energy
Describe the process of conduction
Particles are heated, making them hotter
Particles vibrate more and collide with each other
This transfers energy from their KE stores to other particles which then vibrate faster
What does conduction do?
Transfers energy through objects
What does thermal conductivity describe?
How well a material transfers energy by conduction
Give an example of a type of material with a high thermal conductivity
Metals (Copper)
Give an example of a material with a low thermal conductivity
Gases (Air)
What are ways a house is designed to reduce thermal conductivity?
Double-glazing windows
Cavity walls
Thick walls
How does the thickness of a wall affect the rate of energy transfer?
The thicker the wall, the slower the rate of energy transfer
What is an example of a non-renewable fuel?
Fossil fuels and nuclear fuels
Describe the cost of afossil fuel plant?
Relatively cheap
Describe the cost of a nuclear power plant?
Very costly
What are the disadvantages of non-renewable usage?
Contribution to greenhouse effect
Oil spillages
Risk of nuclear explosion
List examples of renewable energy sources?
Bio-fuels Wind Power Solar Power Hydro-electric Power Tidal Power
What is an advantage of using renewable energy sources?
Don’t damage the environment as much as non-renewable sources
What is a disdvantage of using renewable energy sources?
Don’t release as much energy and not reliable as some depend on the weather
What are biofuels?
Renewable energy resources created from either plant products or animal dung
Why is it arguably carbon neutral?
If you plant trees at the rate you’re burning them
What are the advantages of biofuel?
Reliable
Short time to grow
What are the disadvantages of biofuel?
Can’t respond to immediate energy demands
Very high to refine the fuels
Wasting resources for plants grown for food (water and space)
What are the advantages of wind power?
Low running costs
No pollution
What are the disadvantages of wind power?
Expensive to setup Unsightly and noisy Less efficient than non-renewable Can't respond to high demand Unreliable
What are solar cells made from?
Materials that use energy transferred by light to create and electric current
What are the advantages of solar power?
No running costs
No pollution
What are the disadvantages of solar power?
Expensive to setup
Doesn’t work at night
Can’t respond to high demand
What does HEP usually involve?
Flooding a valley
What are the advantages of HEP?
Immediately respond to increased electricity demand
Low running costs
Reliable
No pollution
What are the disadvantages of HEP?
Loss of habitats
Risk of flooding
Expensive to setup
How does tidal power work?
Tide come’s in to fill up the estuary
Water is then let out through turbines which generates electricity
What are the advantages of tidal power?
No pollution
Reliable
No fuel costs
Low running costs
What are the disadvantages of tidal power?
Affects boat access
Spoils the view
Loss of habitats
Moderately high setup cost
What is most of the UK’s energy produced from?
Non-renewable
Why are smaller energy providers reluctant to change energy source?
It costs money to invest in renewable energy
Why is research into improving the reliability and cost of renewable resources bad?
Costs time and money
Why are personal changes hard to achieve?
Expensive
What do waves transfer?
Energy and infomation
What is the amplitude of a wave?
The displacement from the rest position to a crest
What is the wavelength of a wave?
The length of a full cycle of the wave
What is the frequency of a wave?
The number of complete cycles of the wave passing a certain point per second
What is frequency measure in?
Hertz
What does hertz actually equal?
One wave per second
What is the period of a wave?
The number of seconds it takes for one full cycle
How do you calculate the period of a wave?
Period = 1 / Frequency
Describe the direction of a transverse wave
Perpendicular to the direction the wave travels
Describe the direction of a longitudinal wave
Parallel to the direction the wave travels
Give some examples of transverse waves
Electromagnetic waves
S-waves
Ripples and waves in water
Give some examples of longitudinal waves
Sound waves
P-waves
How do longitudinal waves actually move?
By making compressions (high pressure) and rarefactions (low pressure)
In terms of longitudinal waves, describe compressions
High pressure and lots of particles
In terms of longitudinal waves, describe rarefactions
Low pressure and few particles
What is the wave speed equation?
Wave Speed = Distance / Time
Or
Wave Speed = Wavelength x Frequency
What can you use to measure the speed of sound?
An oscilloscope
Describe how to use an oscilloscope to measure the speed of sound
Line up the microphones so waves align but have moved exactly one wavelength apart
Measure the distance between the microphones to find one wavelength
What can you use to measure the speed of water ripples?
A strobe light
Describe how to use a strobe light to measure the speed of water ripples
Use signal generator to set water waves to a certain frequency
Alter the frequency of the strobe light until the wave pattern on the screen appears to freeze
Then measure the distance between lines that are 10 wavelengths apart then find the average wavelength
What can you use to measure the speed of waves in solids?
Peak Frequency
Describe how to use peak frequency to find the speed of waves in solids
Measure and record the length of a metal rod
Tap the rod with a hammer and write down the peak frequency displayed by the computer
Repeat this three times to get an average peak frequency
Calculate the speed using V = fλ (λ = twice the length of the rod)
What three things can occur when a wave hits a boundary?
Absorbed, transmitted or reflected
What happens to wave when it’s absorbed?
The wave transfers energy to the material’s stores
What happens to wave when it’s transmitted?
The wave carries on travelling through the new material
What happens to wave when it’s reflected?
The wave is sent back away from the second material
How does different density materials affect wave speed?
The denser the material, the slower the wave
What happens to a wave when it hits a boundary at an angle?
Speed and direction changes
What happens to a wave when it hits a boundary along the normal?
Speed change but no change in direction
How does change in speed affect how much a wave bends?
The greater the change in speed, the more a wave bends
When will a wave refract towards the normal?
If it slows down
When will a wave refract away from the normal?
If it speeds up
What affects how much a wave will refract?
It’s wavelength, shorter wavelengths bend more
What doesn’t change during refraction?
A wave’s frequency
What does change during refraction?
A wave’s speed and wavelength
What is the normal?
A line that is at 90* to the boundary
What causes sound waves?
Vibrating objects
What determines what an object can transmit?
It’s size, shape and structure
How are the vibrations in a sound wave passed through?
By a series of compressions and rarefactions
True or False? Sound travels at different speeds in different media?
True
Compare the speed of sound waves in all three of the states of matter?
Solid > Liquid > Gas
Why can’t sound waves travel in space?
Because there are no particles to move or vibrate
Describe how the ear detects sound?
Sound enters eardrum causing it to vibrate
Vibrations passed along to ossicles through the semicircular canals and to the cochlea
Cochlea turns these signals into electrical signals which get sent to your brain
How does frequency affect pitch?
A higher frequency means a higher pitch
What limits the human hearing?
Size and shape of the eardrum
What is ultrasound?
A sound with frequencies higher than 20,000Hz
True or False? Ultrasound is the lowest possible frequency a human can hear?
False
What happens when an ultrasound hits a boundary?
It gets partially reflected
What is partial reflection?
When a wave passes from one medium to another, some of the wave is reflected off the boundary and some is transmitted
What are uses of ultrasound?
Medical imaging and industrial imaging
How is ultrasound used in medical imaging?
Ultrasound waves can pass through the body but whenever they reach a boundary some of the wave is reflected back and detected
The exact time and distribution of these echoes are processed by a computer to produce a videoo image of the foetus
How safe is ultrasound?
As far as we know, it’s completely safe
How is ultrasound used in industrial imaging?
Ultrasound can also be used to find flaws in objects
Ultrasound waves entering a material will usually be reflected
If there is a flaw, the waves will be reflected soon
In sonar, how do you calculate the distance the wave has travelled?
Distance = Speed x Time
In sonar, how do you calculate the depth of the sea?
Distance = (Speed x Time) / 2
What is infrasound?
A sound with frequencies lower than 20
Name some examples of animals that communicate using infrasound
Elephants and whales
Name some uses of infrasound
Animal communication and natural disaster detection
What causes seismic waves?
Earthquakes and explosions
Name two seismic waves
P-waves and S-waves
What can scientists understand through seismic waves?
The structure of the Earth
What type of wave is a P-wave?
Longitudinal
What state can P-wave’s travel through?
Solids and liquids
Describe the speed of a P-wave?
Faster than S-waves
What type of wave is a S-wave?
Transverse
What state can S-wave’s travel through?
Solid
Describe the speed of a S-wave?
Slower than P-waves
True or False? The angle of incidence = Angle of reflection - 180?
False, angle of incidence = angle of reflection
State the law of reflection
Angle of incidence = Angle of reflection
What is the angle of incidence?
The angle between the incoming wave and the normal
What is the angle of reflection?
The angle between the reflected wave and the normal
What is the normal?
An imaginery line that’s perpendicular to the surface at the point of incidence
What is total internal reflection?
When a wave is reflected back into the material
When can TIR occur?
More dense material towards a less dense
When does TIR occur?
When the critical angle is exceeded
What is the critical angle?
The angle of incidence beyond which rays of light passing travel perpendicular to the normal (parallel to the normal)
What are the two types of reflection?
Specular and diffuse
When does specular reflection occur?
When waves are reflected in a single direction by a smooth surface
When does diffuse reflection occur?
When waves are reflected by a rough surface and the waves are reflected in all directions
Why does diffuse reflection occur?
Because the normal is different for each incident ray so each ray has a different angle of incidence and because of angle of incidence = angle of reflection the angle of reflection is different aswell
What do you do with the glass block when investigating refraction?
Trace around it and use a ray box to shine light through it
Once the glass block has refracted the light, what do you do?
Trace the incident ray and the emergent ray and then join up the rays with a straight line
Once all the rays are drawn, when investigating refraction, what do you do next?
Use a protractor to measure the angles and repeat whole experiment and calculate an average
What should you see when investigating refraction?
Ray bends towards normal on entry of the glass and then bends away from the normal on exit of the glass
What does the colour and transparency of a colour depend on?
The wave’s absorbed wavelength
What do opaque objects not do?
Transmit light
What do transparent objects do?
Transmit light
What do translucent objects do?
Absorb and reflect light
How do colour filters work?
They only let through particlular wavelengths of light
What are colour filters used to?
Filter out different wavelengths of light, so that only certain colurs are transmitted
How do secondary colour filters work?
They allow both primary colours that make that colour through
Name the two types of lens
Diverging and converging
Describe the shape of a converging lens
Bulges outwards in the middle
Describe the shape of a diverging lens
Caves inward
What does a converging lens do?
Causes parallel rays of light to be brought together at the principal focus
What does a diverging lens do?
Causes parallel rays of light to spread out
Where is the principal focus in a converging lens?
Where rays hitting the lens parallel to the axis all meet
Where is the principal focus in a diverging lens?
Where rays hitting the lens parallel to the axis appear to all come from
What is the focal length?
The distance from the centre of the lens to the principal focus
What is a virtual image?
An image that is created when light rays appear to be coming from a completely different place to where they’re actually coming from
What is a real image?
An image that is created when light rays come together to form an image
What image can be captured on a screen?
Real
What image can’t be captured on a screen?
Virtual
What increases the power of a lens?
It’s curvature
What lens has a postive power?
Converging
What lens has a negative power?
Diverging
What does a stronger lens mean?
The more strongly it converges rays of light
True or False? Some materials are better at focusing light than others?
True
On a ray diagram, what does a diverging lens look like?
>
On a ray diagram, what does a converging lens look like?
On a diverging lens diagram, how do you locate the virtual image?
Mark the point where the virtual ray meets the ray that goes through the middle
What type of waves are EM waves?
Transverse
True or False? EM waves all travel the same speed everywhere?
False, although they travel at the same speed in a vaccum, they travel at different speeds in different materials
How are EM waves generated?
By changes in atoms and it’s nuclei
How are gamma rays created?
When a positron collides with an electron
How are visible light rays created?
Change in electron energy levels
What do all EM waves transfer?
Energy from a source to an absorber
How do you increase the amount of energy an EM wave transfers?
By increasing the frequency
How do radio waves interact with the human body?
Transmits through without being absorbed
How do micro waves interact with the human body?
Some transmits, however some is absorbed causing the heating of cells
How do visible and infared waves interact with the human body?
Mostly reflected or absorbed by the skin, however, if too much can burn the skin
How do ultraviolet waves interact with the human body?
Is absorbed by the skin, however, due to it’s higher frequency it is dangerous (carcinogenic)
How do x-ray and gamma waves interact with the human body?
Either reflected, transmitted or absorbed as it depends on the deepness of the tissue and can cause mutations and damage to cells
True or False? Only certain objects emit EM radiation, this is because not all atoms are unstable?
False, all objects absorb and emit EM radiation
What does the distribution and intensity of the EM emitted depend on?
The objects temperature
How does temperature change the EM wave emitted?
The hotter the object, the more intense the emitted wavelength
What happens to the radiation emitted to the Earth from the Sun?
Some of it is reflected but most of it is absorbed
Why does it get colder at night?
Because Earth emits it’s radiation which causes a decrease in temperature
How do you investigate what surfaces/colour are better emitters?
Wrap test tubes in the same material but with a different colour or surface
Add boiling water to the test tubes (same volume)
Measure temp (thermometer)
Temperature that drops the most will be best emitter
What are EM waves made up of?
Oscillating electric and magnetic fields
Name one thing made up of oscillating electric charges?
Alternating currents
How can you produce EM waves with an AC?
Make transmitter oscillate to create the radio waves
Reciever absorbs radio waves, energy carried by the waves are transferred to the electrons in the circuit
The current will have the same frequency as the radio wave that generated it (and vice versa)
What is the main use for radio waves?
Communication and broadcasting
Compare long-wave to short-wave radio
Long-wave radio can be recieved halfway around the world this is because they can bend around the curved surface of Earth
Short-wave radio can be recieved from long distances aswell, however, this is because they are reflected by the Earth’s atmosphere
How does bluetooth work?
By sending short-wave radio waves
What type of waves do TV and FM radio use?
Very short radio waves
What do satellites use to communicate?
EM waves
How does a satellite work to transmit TV?
TV sends it’s signal into space where the satellite picks it up and reflects it back to Earth where a satellite dish recieves it
How do microwave ovens work?
By transmitting microwaves that are absorbed by the water molecules in food which then heats the food
How are the microwaves in a microwave different to satellites?
Microwaves in satellites need to pass through the Earth’s watery atmosphere whilst microwaves in microwaves need to transmit through the food a bit and then be absorbed
What are some uses of IR radiation?
To monitor temperature, security systems and transmit infomation
How does IR radiation monitor temperature?
It detects the radiation and transmits it into an electrical signal
How can IR radiation be used to heat foods?
Object emits IR which then transfers into the thermal energy in the object that is being heated
Give some uses of IR radiation when transfering infomation
Optical fibers and TV remotes
What do optical fibers use?
Total Internal Reflection
Give uses of visible light
Photography and vision
Give uses of ultraviolet waves
Fluorescent lights, security pens and the sterilising of water
Give uses of x-rays
Medical imaging and airport security
Why can x-rays be used to “see-through” objects?
Because x-rays are transmitted by flesh but absorbed by denser material (bones or metal)
Give uses of gamma rays
Sterilising, medical imaging and cancer treatment
Why are gamma rays used to sterilise stuff?
Because the gamma rays kill microbes
Why are gamma rays used to treat cancer?
The radiation can be targeted to kill cancer cells
Define a scalar
A quantity with only magnitude, not direction.
Define a vector
A quantity with magnitude and direction
What is the difference between a scalar and a vector?
A scalar has only magnitude and no direction whilst a vector has magnitude and direction
Give examples of a scalar quantity
Speed and distance
Give examples of a vector quantity
Velocity and displacement
What is the acceleration equation?
Acceleration = Change in velocity / Time
What is the uniform acceleration equation?
Final velocity - Inital velocity = 2 x Acceleration x Distance
What does the gradient equal in a distance time graph?
The speed of the object
What does a flat section equal in a distance time graph?
Where the object has stopped
What does a curve equal in a distance time graph?
Where the object is accelerating
What does the gradient equal in a speed time graph?
The acceleration of the object
What does a flat section equal in a speed time graph?
Steady speed
What does a uphill equal in a speed time graph?
Acceleration
What does a downhill equal in a speed time graph?
Deceleration
What does the area under the graph equal in a speed time graph?
The distance covered
What is newtons first law?
If the resultant force on a stationary object is zero, the object will remain stationary. If the resultant force on a moving object is zero, it’ll just carry on moving at the same velocity
What is newtons second law?
The larger the resultant force acting on an object, the more the object accelerated (Force = Mass x Acceleration)
What is newtons third law?
Whenever two objects interact, they exert equal and opposite forces on each other (every action has an equal and opposite reaction)
Why are large decelerations of objects dangerous?
High force required (F=ma)
How can you reduce the risk during large decelerations?
By increasing time (decreasing deceleration)
Give examples of how a car reduces large decelerations?
Seat belts stretch, crumple zones and air bags
Define mass
The amount of matter in an object
What type of quantity is mass?
Scalar
Define weight
The force acting on an object due to gravity
What type of quantity is weight?
Vector
What are the units for mass?
Grams
What are the units for weight?
Newtons
What is the equation for weight?
Weight = Mass x Graviational Field Strength
How does distance from an object affect graviational field strength?
The closer you are to the mass, the stronger the graviational field strength
When an object is travelling in a circular motion, what remains the same?
The objects speed
When an object is travelling in a circular motion, what changes constantly?
The objects velocity (direction)
When an object is travelling in a circular motion, where does the force act towards?
The centre of the circle
When investigating the motion of a trolley on a ramp, what do you measure the mass of?
The trolley, the unit masses and the hook
When investigating the motion of a trolley on a ramp, what do you measure the length of?
The piece of card which interupts the light gate beams
What is inertia?
The tendency for motion to remain unchanged
What does an object’s inertial mass measure?
How difficult it is to change the velocity of an object
Why do objects move although ‘equal and opposite reactions’?
Depends on the mass as (Force / Mass = Acceleration)
So less mass will have a greater acceleration
What is momentum
The amount of oomph an object has
Define momentum
The product of the object’s mass and velocity
What is the equation for momentum?
Momentum = Mass x Velocity
How does the mass of an object affect its momentum?
The higher the mass, the larger the momentum
How does the velocity of an object affect its momentum?
The higher the velocity, the larger the momentum
What type of quantity is momentum?
Vector
What is conservation of momentum?
In a closed system, the total momentum before an event is the same as after the event
If an object has zero velocity, what is it’s momentum?
Zero (Anything times 0 is 0)
What causes changes in momentum?
Forces
What is the equation for change in momentum?
Force = Change in momentum / Time Force = Mass x (Final Velocity - Inital Velocity) / Time
What is the equation for stopping distance?
Stopping Distance = Thinking Distance + Braking Distance
What is the thinking distance?
The distance the car travels in the driver’s reaction time
What is the drivers reaction time?
The time between noticing the hazard and applying the breaks
What affects the thinking distance?
Speed and reaction time (tiredness, drugs and alcohol)
What is the braking distance?
The distance taken to stop once the brakes have been applied
What affects the braking distance?
Speed, mass, condition of brakes and the friction between the car and the road
When measuring reaction times with a ruler, how do you compare results?
The longer the distance, the longer the reaction time
When measuring reaction times with a ruler, why should you do lots of repeats?
Test is extremely inaccurate
What is the reaction time of a typical driver?
One second
To avoid an accident, what must drivers do?
Leave enough space in front so they could stop safely (at least more than the stopping distance)
Why are speed limits important?
Because speed affects stopping distances alot
How does speed affect thinking distance?
As speed increases, thinking distance increases at roughly the same rate (reaction time stays roughly the same)
How does speed affect braking distance?
If speed is times by 2, braking distance will be times by 4 (2²)
What is the equation for work done by the brakes?
Braking force x Braking distance = 1/2x(Mass x Velocity²)
What do electrons sit in?
Different energy levels (shells)
How can a inner electron move to a higher energy level?
By absorbing electromagnetic radiation with the right amount of energy
What has happened when an electron is ‘excited’?
It has moved up to an empty or partially filled shell
What will happen after an electron becomes ‘excited’?
The electron will quickly fall back to its original energy level and in doing so will emit the same amount of energy absorbeb
How is the energy carried away when an electron moves back to it’s original energy level?
By an electromagnetic wave
What does the part of the electromagnetic wave emitted depend on?
The energy
As you get further from the nucleus what happens to the levels?
They get closer together
What happens when an atom is ionised?
It loses an electron (Atom is now positively charged)
What ionises atoms?
Ionising radiation
What is ionising radiation?
Any radiation that can knock electrons from atoms
What are isotopes?
Different forms of the same element
What do unstable isotops do?
Radioactive decay
Why do unstable isotops radioactively decay?
Because they attempt to become stable
What do radioactive substances spit out?
Alpha, beta and gamma radiation but also neutrons
What are alpha particles?
Helium Nuclei (2 protons + 2 neutrons)
How penetrative is alpha radiation?
Not very
What stops alpha radiation?
5 cm of air or a thin sheet of paper
Why is alpha radiation extremely ionising?
Because of its size
What are beta particles?
Either a fast-moving electron or a fast-moving positron
How penetrative is beta radiation?
Moderately
What stops beta radiation?
Meters of air or a sheet of aluminium
Which type of beta radiation has a shorter range?
Positive because it contains positrons and when they hit an electron they destroy each other and produce gamma rays
What are gamma rays?
High frequency, low wavelength electromagnetic wavess
How penetratative is gamma radiation?
Extremely as they penetrate far into materials without being stopped
What stops gamma radiation?
Thick sheets of lead or meters of concrete
When is gamma radiation created?
When a nucleus decays and it undergoes nuclear rearrangement and releases energy
What are nuclear equations ways of showing?
Radioactive decay
How are nuclear equations written?
Atom before decay -> Atom after decay + Radiation emitted
What is the one ‘golden rule’ with nuclear equations?
The total mass and atomic numbers must remain equal on both sides
How does alpha decay affect the atom?
Decreases the charge and mass of the nucleus (by 2 and then 4)
How does beta-minus decay affect the atom?
Increases the charge of the nucleus
How does beta-plus decay affect the atom?
Decreases the charge of the nucleus
How does neutron emission affect the atom?
Decreases the mass of the nucleus
How are beta-minus particles formed?
A neutron turns into an electron and proton
Electron then leaves nucleus
How are beta-plus particles formed?
A proton turns into an neutron and positron
Positron then leaves nucleus
True or False? Radioactivity is a totally random process?
True
What do radioactive sources contain?
Radioactive isotopes that give out radiation from the nuclei of their atoms
What is activity?
The rate at which a source decays
What are the units for activity?
Becquerels (Bq)
What does 1 becquerel equal?
1 decay per second
How can you measure activity?
By using a Geiger-Muller tube and counting the amount of clicks
What happens each time a radioactive nucleus decays?
One more radioactive nucleus disappears which causes the activity as a whole to decrease
What is half-life?
The average time taken for the numer of radioactive nuclei in an isotope to halve
What does a short half-life mean?
The activity falls quickly
What does a long half-life mean?
The activity falls slowly
Where does background radiation come from?
Human activity, space, food, buildings and rocks
What is the absorbed radiation dose?
The amount of radiation you’re exposed to
What are ways of reducing irradiation?
Lead-lined boxes, barriers and remote-controlled arms
Why is contamination of unwanted radioactive atoms bad?
If they get stuck, they will decay and release radiation
When are contaminated people at risk of harm?
Until the source is removed or all the atoms have decayed
How does radiation damage cells?
Radiation will ionse the atoms and molecules within the cells
How do lower doses affect cells?
Cause minor damage without killing the cells or mutation of cells
How do higher doses affect cells?
Kill cells completely causing radiation sickness (vomitting, tiredness and hair loss)
Compare the risk of radiation outside the body
Beta and gamma are the most dangerous with alpha being less dangerous as it can’t penetrate the skin
Compare the risk of radiation inside the body
Alpha sources are the most dangerous as it’s the most ionising
What radiation has the biggest risk with contamination?
Alpha
What radiation has the biggest risk with irradiation?
Beta or gamma
How does activity affect the danger of a radiation?
The higher the activity, the more dangerous the radiation
When choosing a radioactive source for an application, what must you look for?
Look to find a balance between a source that has the right level of activity but also the right half life
How do fire alarms work?
Uses weak source of alpha radiation and two electrodes
Source causes ionisation and a current flows
If there is a fire the smoke will absorb the particles and prevent the current
Why can gamma rays be used to steralise?
A high dose of gamma rays will kill all microbes
Why is irradiation better than boiling?
Irradiation doesn’t involve high temperature which would ruin fresh ruit or plastic instruments
What would the radioactive source be like for sterilisation?
Strong emitter and long half-life
What isotopes must be put into a body?
Only gamma and beta (never alpha, unless for cancer treatment)
What would the radioactive source be like for tracers?
Short half-life
How else is gamma used?
To detect leaks in underground pipes
How else is beta radiation used?
Thickness control
Why must beta radiation be used when measuring thickness control?
Because gamma will completely transmit through but also alpha won’t even make it to the object
What is PET scanning a technique for?
To show tissue or organ function and diagnosis of medical conditions
What do you inject into the patient?
A substance used by the body with a tracer
What occurs once the substance is injected into the patient?
The positrons will be emitted which will them meet electrons and annihilate which will then emit gamma rays
How can a tumour be found in a PET scan?
By triangulation
What types of radiation are used to treat tumours internally?
Alpha and beta
What types of radiation are used to treat tumours externally?
Gamma
Describe the half-life of internal treatment of tumours
Short to limit the amount of exposure time
Describe the half-life of external treatment of tumours
Long to prevent the need to replace
What is nuclear fission?
The splitting up of big atomic nuclei
What is nuclear fission used to do?
Release energy from uranium atoms
Describe the process of nuclear fission
A slow-moving neutron is fired at a large, unstable nucleus
The nucleus absorbs the nuetron and causes it to split
What is created when U-235 splits?
Two new lighter elements (daughter nuclei and energy)
How is nuclear fission a chain reaction?
When the uranium atom splits up, it also spits out two or three neutrons which can hit other uranium nuclei
What is the name of the slow-moving neutrons in nuclear fission?
Thermal neutrons
How are neutrons slowed down?
By placing the fuel rods in a moderator
How do control rods work?
Limit the rate of fission by absorbing excess neutrons
What would happen if nuclear fission was left?
Large amounts of energy would be released resulting in a runaway reaction which could cause an explosion
What is nuclear fusion?
The joining of small nuclei
True or False? The mass of the heavier nucleus equals the mass of the two seperate, light nuclei?
False, because some of the mass is converted to energy
What conditions must fusion occur in?
High temperature and pressure
What temperature is needed for fusion?
10,000,000*C
Why is such a high temperature needed for nuclear fusion?
To overcome the high electrostatic repulsion as the positively charged nuclei have to get very close
Why is it really hard to create the right conditions for fusion?
No material can withstand that kind of temperature
What are the pros of nuclear power?
Pretty safe Very reliable Doesn't release bad gases (clean source) Huge amounts of energy released Nuclear fuel is cheap and readily available
What are the cons of nuclear power?
Poor public perception
Hard to dispose of waste products
Risks of leaks
Overall cost is extremely high
