Waves Flashcards
What must the frequency of a sound wave be greater than to make it an ultrasound
20,000 Hz
2 types of reflection
Specular
Diffuse
Which type of reflection requires a rough surface
Diffuse
Which type of reflection requires a smooth surface
Specular
What can happen to light when it meets a new medium
Reflection, refraction, transmission, absorbtion
What do waves transfer from one place to another
Energy
True or false, waves transfer matter from one place to another
False, they transfer energy
True or false, waves transfer energy from one place to another
True
Which out of energy or matter do waves transfer from one place to another
Energy
To travel from one place to another the waves vibrate/ what
Oscillate
Another word for oscillate
Vibrate
What do waves do when they travel from one place to another
Oscillate/ vibrate
Word for maximum displacement (distance between undisturbed ‘sea’ level and highest/ lowest point of wave
Amplitude
True or false, one entire oscillation is equivalent to the wavelength
True
What is meant by time period of wave
Time it takes for one complete wave to pass a fixed point
Difference between wavelength on displacement distance graph vs displacement time graph for wave
Displacement time- wavelength represents time period (how long it takes for 1 oscillation/ 1 wave to pass)
Displacement distance- wavelength still represents oscillation but with no reference to how long it takes
True or false, 1 complete oscillation = 1 full wave
True
What is meant by frequency of wave
Number of complete waves per second
Name for number of waves per second
Frequency
Frequency vs time period
Frequency= number of waves per second
Time period= time taken for one complete wave to pass a fixed point
What unit is wavelength measured in
Metres
What unit is wave speed measured in
M/s
2 main types of wave
Transverse
Longitudinal
In transverse waves the oscillations are what to the direction the wave is moving
Perpendicular
In longitudinal waves the oscillations are what to the direction the wave is travelling
Parallel
In what type of wave are the oscillations parallel to the direction the wave is travelling
Longitudinal
In what type of wave are the oscillations perpendicular to the direction the wave is travelling
Transverse
True or false, the direction of energy transfer is the same as the direction the wave is moving
True
Are all electromagnetic waves longitudinal or transverse
Transverse
True or false, all electromagnetic waves are longitudinal
False
They’re all transverse
What type of wave are sound waves
Longitudinal
2 examples of longitudinal waves
Sound waves
P- seismic waves
Name for type of diagram used to show reflection taking place
Ray diagram
In reflection the angle of incidence is always equal to what angle
The angle of reflection
In reflection what 2 angles are always equal
Angle of reflection
Angle of incidence
Name for dashed line drawn perpendicular to boundary in ray diagram
Normal
What is the normal
Dashed line drawn perpendicular to boundary in ray diagrams
Should the normal be a solid or dashed line
Dashed
In reflection if the angle of reflection is 45 degrees then what’s the angle of incidence
45 degrees
(As they’re always equal)
In reflection which angle are are we already given/ have to measure
Angle of incidence
(Check answer)
What is the ‘point of incidence’
Point in ray diagram for reflection where incoming ray (incident ray) meets the boundary
What type of reflection is a mirror and why
Specular reflection
Mirror is a smooth surface so all rays come in at same angle and therefore are reflected at the same angle (normals are all in same direction)
What type of reflection is paper
Diffuse
(As it has a rough surface, even though it doesn’t seem like it)
What type of reflection is paper
Diffuse
(As it has a rough surface, even though it doesn’t seem like it)
True or false, in both specular (smooth surface) and diffuse (bumpy surface) reflection the light rays are all coming in from the same direction
True
However in diffuse reflection the normals will all be pointing in different directions as they have to be perpendicular to the surface which isn’t the same everywhere, therefore the light will be reflected in lots of different directions
Why is light reflected in lots of different directions in diffuse reflection
The normals are all pointing in different directions due to the surface being bumpy and they have to be 90 degrees to the surface (so even though the waves all come from the same direction, they will have to be reflected off in different directions)
Which type of reflection produces a clear image
Specular
True or false, in both Specular and diffuse reflection the angle of incidence is always equal to the angle of reflection
True
Waves travel at different what in different materials
Speeds
Why do waves travel at different speeds through different mediums
Different materials have different densities
Do waves travel faster or slower in denser materials
Slower
In what type of material do waves travel fastest
Low density
(They travel slower in higher densities)
Another word for material
Medium
If a wave travels from a less dense medium to a more dense medium what happens to its speed
Slows down
(As waves travel slower in higher densities)
Which is more dense out of air and glass
Glass
(so waves will travel slower in glass than air)
If a wave travelling from air into glass hits the boundary at a perpendicular angle then what happens
It will keep travelling straight through but just change speed due to the different densities
(It will only be refracted if it comes in to the boundary at an angle)
In what scenario will the wave bend towards the normal
Going from less dense to more dense
When a wave enters a more dense medium does it bend towards or away from the normal
Towards
When a wave enters a less dense medium does it bend towards or away from the normal
Away
When does a wave bend towards compared to away from the normal
Going into more dense= bends towards normal
Going into less dense= bends away from normal
True or false, when waves enter a different medium their wavelength also changes
True
As wave speed = frequency x wavelength
And frequency always stays the same
Does the frequency of the wave ever change
No
Does the wavelength of the wave ever change
Yes
When the wave passes through a different medium and changes speed as frequency never changes and
Wave speed= frequency x wavelength
When the wave speed changes e.g passing through a different medium which other aspect of the wave also changes
Wavelength
(As wave speed = frequency x wavelength)
(Frequency never changes)
When electromagnetic waves are travelling through a …, they all travel at the same speed
Vacuum (or air)
What speed do all EM travel at through a vacuum/ air
3 x10^8 m/s
7 types of EM waves
Radio waves
Microwaves
Infra-red waves
Visible light
Ultraviolet rays
X rays
Gamma rays
Electromagnetic waves transfer energy from what to what
Source, absorber
2 things EM waves are grouped by
Wavelength, frequency
Which EM wave has the highest frequency (and therefore shortest wavelength)
Gamma rays
Which EM waves have the lowest frequency (and therefore longest wavelength)
Radio waves
True or false, electromagnetic waves form a continuous spectrum
True
Which is the only type of EM wave humans can see
Visible light
2 uses of radio waves
Radios
TVs
2 uses of microwaves
Cooking food
Satellite communication
4 uses of infrared waves
Remote controls
Toasters
Electric heaters
Thermal image cameras
1 use of visible light waves
Fibre optic communications
2 uses of ultraviolet waves
Sun tanning
Security marking (e.g on passports/ banknotes)
2 uses of X- rays and gamma rays
Medical imaging
Medical treatment
What type of wave is used for medical imaging and treatment
Both X-rays and gamma rays
Type of wave used for fibre optic communications
Visible light
Type of wave used for sun tanning and security marking
Ultraviolet
Type of wave used for radios and TVs
Radio waves (hence name)
Type of wave used for cooking food and satelite communication
Microwaves
(Although infrared can also be used for cooking food in toaster)
Type of wave used for remote controls, cooking food (toaster), thermal image cameras and electric heaters
Infrared
2 types of wave used to cook food
Microwaves (microwave)
Infrared (toaster)
Which type of EM wave can damage eyesight due to being very bright
Visible light
Hazard of visible light
Very bright so can damage eyesight
Hazard of ultraviolet waves
Can cause skin cancer/ premature skin ageing
Which type of wave can cause skin cancer/ premature skin ageing
Ultra violet
Which type of wave can cause burns
Infrared
Hazard of infrared waves
Can cause burns
Hazard of X-rays and gamma rays
Ionising radiation can cause cancer (but also treat it)
Which type of wave can cause cancer (but also treat it)
X-rays and gamma rays
Refractive index of glass
1.5
(Ratio quantity so no unit)
Precision meaning
How close measured values are to the mean
Name for how close measured values are to the mean
Precision
Accuracy vs precision
Precision= how close measured values are to mean
Accuracy= how close measured values are to actual value
What do EM waves transfer from their source to absorber
Energy
.
.
Why are microwaves suitable for cooking food and satellite communications
Can pass through Earth’s atmosphere to reach satellites
Can penetrate into food and are absorbed by the water molecules so heat it
Why are infrared waves suitable for electric heaters, TV remotes, thermal image cameras and toasters (cooking food)
Can transfer energy quickly (so good for heating room/ food)
All hot objects emit this type of wave (infrared) so sensors can detect these to turn it into an image
Why is visible light useful for fibre optic communications
Have short wavelength so can carry more information
Why are X-rays and gamma rays good for medical imaging and treatment
Pass easily through flesh (but not denser materials like bones)
High dose kills living cells like cancer cells
3 types of radio wave
Long wave
Short wave
Very short wave
Which type of radio wave can be transmitted (passed from one place to another) long distances
Long waves and short waves
Why can long waves (type of radio wave) be transmitted long distances
They diffract (bend) around the Earth’s surface
What type of radio wave diffracts (bends) around the Earths surface
Long waves
Why is it good if long waves (type of radio wave) can diffract (bend) around the earths surface
They can travel long distances
True or false, both long waves and short waves (types of radio waves) can bend around the Earth
False
(Only long waves can)
Which type of radio wave can diffract around the Earth’s surface
Long waves
Which type of radio wave are reflected off the ionosphere (electrically charged layer of Earth’s upper atmosphere)
Short waves
Ionosphere meaning
Electrically charged layer of Earth’s upper atmosphere
Name for electrically charged layer of Earth’s upper atmosphere
Ionosphere
Diffract meaning
Bend
E.g long waves (radio waves) diffract around the earth’s surface
True or false, although short waves (radio waves) can travel long distances they can also be used to cover short distances
True
(E.g bluetooth)
Example of short waves (radio waves) being used for short distance
Bluetooth
Which type of radio wave is used for Bluetooth
Short wave
What are very short radio waves used for
TVs and radios
Which type of radio waves are used for TVs and radio
Very short waves
Which type of radio wave travels directly from the transmitter to receiver
Very short waves
Why is it bad in very short radio waves that they travel directly from the transmitter to the receiver
Tunnels/ hills etc can get in the way and make the signal bad e.g when you’re listening to the radio in the car
Type of radio wave that can only travel in straight lines
Very short wave
(Long waves can bend around the Earth’s surface and short wave are reflected back and forth off the ionosphere)
What type of current do radio waves create when they are absorbed by the receiver
Alternating current
Use of oscilloscopes
Display frequency of an alternating current
True or false, all microwaves can be absorbed by water molecules
False
Only some can
Which type of microwaves are used for communications (satelites)
Ones that can’t be absorbed by water
Why can only microwaves that aren’t absorbed by water be used for satelites
Satelites are high above the Earth
For the wave to get to the satelite it therefore needs to pass though the Earth’s atmosphere but the atmosphere contains water vapour
If it was absorbed by water vapour it would never reach the satelite
How do microwaves work in heating up our food
Nearly all food contains water molecules so microwaves are used that can be absorbed by water
The microwaves are fired at our food
Energy from waves is absorbed by water molecules in food
Water molecules start to vibrate more so pass on energy to neighbouring non- water molecules
Energy then spreads through food by convection/ conduction
What important molecule do foods contain that allows them to be heated up by microwaves
Water molecules (this is what absorbs the wave to allow the energy to be transferred)
What in the food absorbs the microwave
Water molecule
Why do foods higher in water heat up faster in microwaves
Water is what absorbs the wave
So the energy can be absorbed quicker and therefore spread through food quicker as more particles are vibrating
True or false, microwaves can pass through the atmosphere
True
This allows them to reach satelites
How do microwaves work in communication
Wave passes up through atmosphere to satelite
Satelite then sends signal back down to other point on earth that you’re communicating with (can be used to communicate with people on other side of world)
If an object is hotter will it emit more or less infrared radiation
More
For thermal imaging cameras will hotter objects that emit more infrared radiation (e.g animals/ criminals) be brighter or darker
Brighter
Visible light appears different colours depending on the what
Wavelength
Which colour of visible light is the has the longest wavelength
Red
(Violet is the shortest)
What are optical fibres (used in fibre optic communications)
Thin glass/ plastic fibres that transmit pulses of light over long distances
(As the light is reflected every time it hits the surface of the fibre so just keeps on moving)
Can optic fibres transmit light over long distances. Why/ why not
Yes
Optic fibre is very thin fibre of plastic/ glass- light is repeatedly reflected off surface so keeps going whole way through until it emerges out of the fibre
Are fibre optic communications fast or slow
Fast
Advantage of using optical fibres instead of copper wires (electricity)
Optical wires can transmit much more information
+ signals less likely to be distorted during transmission
Why does UV light sterilise water
It kills microorganisms like bacteria
How do X- rays work
X-rays are fired at patient
X-rays are absorbed by dense materials e.g bones
X-rays are transmitted through less dense materials e.g lungs/ intestines
The X-rays that pass through are detected by a detector plate to form an X-ray image
Gamma rays are produced by changes in the what in the atom
Nucleus
Radio waves are produced by what in an electrical circuit
Oscillations
Radio waves are produced by oscillations in a what
Electrical circuit
2 areas created on longitudinal wave due to the particles being squashed closer together/ pulled further apart
Rarefaction
Compression
What is a wave
A disturbance that transfers energy from one region of the system to another
Name for where air particles are squashed together in longitudinal wave
Compression
Name for where air particles are spread apart in longitudinal waves
Rarefaction
What frequency can humans hear between
20 Hz and 20,000Hz
2 types of seismic waves
P- waves
S- waves
Which type of seismic waves are transverse and which are longitudinal
P- waves= longitudinal
S- waves= transverse
Type of seismic wave that pushes and pulls material
P- waves
(As they’re longitudinal)
Type of seismic wave that shakes material side to side
S- wave
Can S- waves travel through a liquid
No, only a solid
Which type lf seismic wave can travel through solids only, not liquids
S- waves
Which type of seismic wave can travel through both solids and liquids
P- waves
Seismologists use data received at monitoring stations around the Earth to do what
Determine size of core
Determine structure of Earth
Which layers of the earth are liquids and which are solids out of inner core, outer core, mantle and crust
Inner core, mantle and crust = solid
outer core = liquid
Which type of seismic wave can’t pass through the outer core and why
S- waves
Outer core is liquid
S- waves can only travel through solids not liquids
Each colour in the visible light spectrum has its own narrow band of what
Wavelength and frequency
3 primary colours
Red
Blue
Green
3 secondary colours
Cyan (blue/ green)
Magenta (purple/ pink)
Yellow
Colour filters work by absorbing certain what and transmitting other wavelengths (colours)
Wavelengths (and therefore colours as different colours have different wavelengths)
How do colour filters work
Absorb certain wavelengths (and therefore colours)
Transmit other wavelengths (and therefore colours)
Why don’t white or black appear on the visible light spectrum
Black is simply the absence of (visible) light
White is a combination of all the wavelengths (colours)
Purpose of ripple tank RPA
Measure speed of wave in a liquid
The ripple tank RPA measures the speed of a wave in a what
Liquid
Wave speed RPA measuring frequency and wavelength method
1) set up a ripple tank and turn on the overhead lamp and electric motor
2) place a 30cm ruler in the ripple tank perpendicular to the oscillating paddle (so that it’s perpendicular to the direction the waves are travelling)
3) Take a picture of the projected image
4) Use the ruler to measure the wavelength of 10 waves and divide by 10 to find mean wavelength (improves accuracy)
(Now you have wavelength)
1) Place a stopwatch next to the ripple tank
2) Take a slow motion video of the waves moving alongside the stopwatch
3) Count the number of waves that pass a fixed point in 10 seconds using the stopwatch in the video
4) Divide number of waves counted in 10s by 10 to get frequency (number of waves passing fixed point per second)
(Gets frequency)
Multiply frequency by wavelength to get wave speed
Wave speed RPA all in one method
1)Set up ripple tank and turn on overhead lamp and electric motor
2)place ruler next to tank perpendicular to the oscillating paddle
3) Place stopwatch next to tank
4) Turn on stopwatch and take slow motion video with stopwatch in
5) Mesure length of tank with ruler
6) Using slow motion video measure time it takes for 1 wave to travel length of tank
7) Calculate wave speed by doing distance/time
8) To improve accuracy repeat whole process to find mean wave speed and reduce effect of random errors
In wave ripple tank RPA why are all the wave speeds similar but not identical
Although waves move at the same speed in water it’s hard to see exactly where the waves are and be 100% accurate with measurements as the waves keep moving and some are reflected
