Physics Higher 4 GCSE Flashcards
What are waves
Vibration of atoms
Longitudinal waves
The direction of the movement of the particles is equal to the direction of the wave
Transverse waves
The direction of the movement of the particles is at 90 degrees to the direction of the wave
Difference between electromagnetic and mechanical waves
Mechanical waves need matter to travel through, but EM waves don’t
What is a time period of a wave
The time it takes for the wave to finish one wave
equation for wave velocity
wave velocity(m/s) = frequency (Hz) * wavelength (m)
How to measure the velocity of sound
You can time how long it takes to hear an echo of a clap when you are at a distance from a wall, you can work out the velocity of the clap too.
OR
You can connect a pair of microphones a certain distance apart to an oscilloscope.
What happens to sound waves when it travels across a boundary
When a wave travels from one medium to another, its velocity can change as well as its direction. This is called rarefaction
What happens to a sound wave at a boundary
the sound can be:
reflected
transmitted
absorbed
what is ultrasound
sound of a frequency higher than 20,000 Hz. This means that we can’t hear it, but other animals can
Uses of ultrasound
In pregnancy scans
Transmitter beams ultrasound into the mother
The waves reflect at different boundaries
The machine calculate using the time and velocity, to produce an image
Can also be used for echo-sounding and sonar
How does an ear work- explanation
As the sound travels to the eardrum, and it vibrates, it makes the ossicles vibrate. They act like levers to amplify the vibration and pass it on to the inner ear through the oval window.
The cochlea contains fluid which transmits the movements of the oval window to small hairs on the inside wall of the cochlea. These hairs are attached to sound-detecting cells that release chemical substances, which sends a signal to the brain using nerves.
EM spectrum
(increasing frequency)
Radio waves, microwaves, infrared, visible light, UV, X-Rays, gamma rays
What wave is an EM wave
a transverse wave
it has oscillating electric field and magnetic fields.
How are radio waves produced and detected
An oscillating pd across a wire makes electrons move back and forth. This produces a changing electric and magnetic field, which is emitted as a radio wave.
When the fields meet another metal, this makes the electrons move, producing an electrical signal. EM waves are also produced by the movement of electrons in atoms
what is the speed of an EM wave
It always travels at 3 * 10 to the power of 8
What is a CCD image
A charge-coupled device
How are gamma rays used for imaging
A doctor injects the patient with a radioactive substance that emits gamma rays.
Ionosphere
High frequency radio waves pass through the ionosphere, but lower frequency ones are reflected.
What is the description of a concave lens
Virtual, diminished, upright
Examples of concave lenses
Spy holes in doors
Back windows of coaches
Examples of convex lenses
Magnifying glass (virtual, magnified, upright)
Camera, Eye (real, diminished, inverted)
Projector (real, magnified, inverted)
Microscope (real, inverted)
When is an image virtual
If it is made on the same side as the actual object
What are the 2 types of reflection
Specular- gives a sharp image
Diffuse- Blurry image
Why do atoms emit radiation
Because they are unstable.
What is alpha radiation
a helium atom’s nucleus
What is beta radiation
a fast moving electron
How can you detect radiation
Using a Geiger counter. A device that clicks when radiation enters it.
What is alpha radiation stopped by
air or paper
What is beta radiation stopped by
Aluminium
What is gamma radiation stopped by
Lead or concrete
What is ionising power
The radiation emitted by radioactive material, meaning that the radiation can remove electrons to form ions
What is the ionising power of all 3 radiation
Alpha: high
Beta: medium
Gamma: low
Calculating with half life
- find the number of half lives in the days ( days/ half life)
- use that to calculate the new activity. (1/2 multiplied by itself the new activity number of times)
- multiply that number by the original activity
What is the absorption spectrum
The set of frequencies of radiation absorbed by an atom when it is excited and the electron moves to a higher shell
What is the emission spectrum
The set of frequencies of radiation emitted by an atom when the electron moves to a lower shell
Nuclear Fission
A larger nucleus splits into fragments and emits neutrons. It needs a neutron to start the reaction. In each splitting, more neutrons are fired out, to continue the chain reaction
Nuclear Fusion
When 2 nuclei join. It requires a lot of energy and pressure, can only be done on the Sun so far.
Releases energy through e= change in mass *speed 2
types of stores
chemical kinetic thermal gravitational nuclear electrostatic magnetic
Thermal conductivity
The lower the thermal conductivity, the less heat it will conduct. So better for walls
how to increase efficiency
use insulation to reduce wasting heat
make devices from materials that reduce unwanted heat transfer
use technologies that are better at their job
when a ball is dropped, how does its energy store change
before: lots of gravity store
after: lots of kinetic store
when a spring is pulled, how does its energy store change
before: less energy in its chemical store
after: more energy in its elastic store
when a car stops or slows down, how does its energy store change
before: energy in kinetic store is low
after: energy in thermal store increases
when you lift an object, how does its energy store change
before: energy in kinetic and chemical store is low
after: energy in gravity store increases
when you use a kettle, how does its energy store change
before: energy in chemical store is low
after: energy in thermal store increases
average speed of someone walking
1 m/s
average speed of someone running
5 m/s
average speed of someone cycling
7 m/s
average speed of a car
22 m/s
average speed of a train
56 m/s
what factors affect thinking distance
drinking alcohol drugs tiredness eating or drinking radio distraction by others
equation for force
force= mass * acceleration
non renewable energy sources
fossil fuels
nuclear fuels
renewable energy sources
solar wind waves geothermal HEP
what fuels are generally used for heating
fossil
biofuels
solar
geothermal
what fuels are generally used for transport
fossil
biofuels
what factors need to be considered when deciding on energy sources
cost
effect on the environment
contribution to climate change
how long the sources last
what are the 3 wires in a plug
live wire- brown
neutral wire- blue
earth wire- green and yellow
earth wire: not connected t the mains, It is connected to a large metal pole buried into the ground outside your house.
what is mains voltage
230 V at a frequency of 50 Hz
What safety features are in the plugs
if the live wire becomes loose, it could touch the metal casing and then the casing carries a pd of 230 V. To prevent this, the earth wire connects to the earth to transport the current to the earth instead because it has less resistance than you. Also, the wire inside the fuse melts and switched off the circuit.
Or these cases can be made out of plastic, which can’t conduct electricity.
what is red shift
There is an observed increase in the wavelength of the light from distant galaxies where the light is shifted towards the red end of the spectrum.
Who came up with the red-shift theory
Edwin Hubble. He measured the speed of galaxies from the absorption spectrum.
What is the Big Bang model
The idea that the universe started from something extremely dense and expanded suddenly 13.7 billion years ago. They believe that the universe is still expanding.
Evidence for the Big Bang model
There is Cosmic Microwave Background Radiation, which was left after the Big Bang.
4 inner rocky planets
Mercury, Venus, Earth and Mars
types of orbits
geostationary orbit: 24 hours for one orbit and it stays fixed above the Earth’s equator. used for communications and TV.
low polar orbit: 2 hours for one orbit. Orbits over the poles for military spying and weather.
Relationship between temperature and radiation
The hotter the object, the higher the frequency of radiation it will emit.
When does the temperature of an object increase
if it emits less radiation than it absorbs, the temperature increases
When does the temperature of an object decrease
if it emits more radiation than it absorbs
Structure of the Earth
Solid inner core
Liquid outer core
Mantle can flow
Solid crust
What are shadow zones
The shadow zone is the area of the earth from angular distances of 104 to 140 degrees from a given earthquake that does not receive any direct P waves. The shadow zone results from S waves being stopped entirely by the liquid core and P waves being bent (refracted) by the liquid core
S-waves
Transverse- cannot travel through liquids
P-waves
Longitudinal- travels through solids and liquids
What to keep in mind when drawing a ray diagram
Will it bend towards or away from the normal?
What to do if there is a circular glass block?
The side that meets the curved side actually shouldn’t refract at all . This is because it is travelling along the radius of the circular shape, and all radii meet the circumference at 90 degrees
Why does the emergent light disperse into different colours?
White light is actually made up of many wavelengths of lights, which we see as different colours. When these different wavelengths enter the glass block, they refract by different amounts. Shorter wavelengths of light refract more than longer wavelengths. Therefore causing the colours to separate slightly. Red light has the longest wavelength and violet has the shortest wavelength, so these colours may be seen with other colours in the middle.
how does night vision cameras work
they detect the objects because of its temperature difference to the surroundings
how do x-rays generate an image of a bone
X-rays are absorbed by the bones in the body but transmitted by other muscles and tissues. It is shot towards a detector plate. Where there is low X-ray, it has been absorbed by bones.
how is visible light used to transmit phone signals
the phone signal is converted into a series of light pulses, which are sent in an optical fibre. They repeatedly reflect off of the side of the cable till they reach the end.
reasons for the increased risk of cancer
increased UV radiation. You are protected by the Earth’s atmosphere but not on other planets.
advantages of CT scans
show more detail than ultrasound
give a clearer image
can be used to show both tissues and bones
are ultrasound waves ionising?
no
are x rays ionising
yes
are infrared imaging ionising
no
explain how infrared imaging works
it detects the amount of infrared radiation being given out of the body. The amount of infrared radiation increases as the temperature increases. This is then used to create an image
advantages of gamma compared to ultrasound
gamma radiation can go through bones and detect tumours anywhere in the body
disadvantages of gamma compared to ultrasound
gamma can cause cancer, but ultrasound can’t
3 ways in which energy is transferred
radiation
conduction
convection
Explain how adding oil reduces energy loss
it increases efficiency because the oil acts as a lubricant, reducing friction. Therefore, it will reduce unwanted energy transfer through heating
what is the power rating
the energy transferred to an appliance per second
How to calculate the period of a wave
Period = 1 / frequency
How is heat / energy transferred?
Radiation
Convention
Conduction
At what state does convection happen in
Gases
At what state does conduction happen in
Liquids and maybe solids?
Ways that you could make your house more energy- efficient?
Loft insulation reduces energy loss by convection and conduction
Hot water tank could be fitter with an insulating jacket to keep the water hot
Windows could be double glazed to prevent the loss of heat through conduction and convection.
Cavity walls could be filled with insulating foam
Central heating pipes could be covered in insulating material as well to reduce heat loss
Central heating system pipes coil die painted white to reduce the energy transferred away by heating
What is the power rating
The energy transferred to an appliance per second
What happens when you increase the height of dropping an object
As height increases, the gravitational potential energy increases too. This means the speed of the object being dropped increases too, therefore the kinetic energy increases.
Why may the speed be lower than what is calculated
In the measurements, we ignore the effects of air resistance. So the actual speed is much lower because of air resistance that slows it down
Explain how the red shift of light from distant galaxies provides evidence for the Big Bang model
Measurement of red shifts show all the galaxies are moving away from the Earth and that the more distant a galaxy is, the faster it is moving away and therefore showing a greater red shift. Something must have initially started them moving and this is likely to be the Big Bang.
explain why some objects glow red when they are heated
As the temperature of an object increases, the intensity of every emitted wavelength increases. However, the intensity increases more for shorter wavelengths, than longer ones. So as objects get hotter, the peak wavelength gets shorter and moves towards the red end of the visible spectrum showing red light.
how is temperature and intensity related
as the temperature increases, the intensity of each emitted wavelength in increased.
why does the intensity increase more for shorter wavelengths
because shorter wavelengths of EM radiation have a higher frequency and transfer more energy. This means the peak wavelength (the most common wavelength) to decrease.
why do hot materials cool down
because they emit more radiation than they absorb, eventually cooling down
why do cold materials get hotter
because they absorb more radiation than they emit, eventually warming up.
