Physics Waves Topic Flashcards
Waves may be either
The ripples on a water surface are an example of a
transverse or longitudinal.
transverse
wave.
Longitudinal waves show areas of:
Sound waves travelling through air are
compression and rarefaction.
longitudinal.
describe the difference between
longitudinal and transverse waves.
In transverse waves the oscillations are perpendicular (at 90 degrees) to the direction of energy transfer. For example a spring wiggled from side to side gives a transverse wave. In longitudinal waves, the oscillations are parallel to the direction of energy transfer. If you push the end of a spring,you get a longitudinal wave.
Amplitude of a wave:
the maximum displacement of a point on the wave from its undisturbed postion
The wavelength:
is the distance from a point on one wave
to the equivalent point on the adjacent wave
a period
The period of a wave is defined as the time it takes for one complete cycle of the wave (one wavelength) to pass a given point. .
Frequency
the number of waves passing a point
each second.
Period equation
frequency in
1/frequency
hertz
The wave speed is
the speed at which the energy is transferred (or
the wave moves) through the medium.
wave speed equation with units of measurement
wave speed = frequency × wavelength
v = f λ
wave speed, v, in metres per second, m/s
frequency, f, in hertz, Hz
wavelength, λ, in metres, m
- describe a method to measure the speed of sound waves in
air
By attaching a signal generator to a speaker you can generate sounds with a specific frequency . You can use two microphones and an oscilloscope to find the wavelength of the sound waves generated
1. Set up the oscilloscope so the detected waves at each microphone are shown as separate waves
2. Start with both microphones next to the speaker, then slowly move one away until the two waves are aligned on display, but have moved exactly one wavelength apart
3. Measure the distance between the microphones to find one wavelength
4. You can then use the formula v = f λ
to find the speed (v) of the sound waves passing through air- the frequency (f) is whatever you set the signal generator to (around 1 Khz is sensible)
describe a method to measure the speed of ripples on a water
surface.
Using a signal generator attached to the dipper of a ripple tank, you can create water waves at a set frequency
1) Dim the lights and turn on the lamp- you’ll see a wave pattern made by the shadows of the wave crests on the screen below the tank
2) The distance between each shadow line is equal to one wavelength. Measure the distance between the shadow lines that are 10 wavelengths apart, then divide this distance by 10 to find the average wavelength. This is a suitable method for measuring small wavelengths
3) If you’re struggling to measure the distance, you could take a photo of the shadows and ruler, you find the wavelength from the photo instead
4) Use v = f λ to calculate the speed of waves
5) This set-up is suitable for investigating waves, because it allows you to measure the wavelength without disturbing the waves
Waves can be reflected at the
boundary between two different materials
Waves can be absorbed or
transmitted at the boundary between two different materials
Reflection
When a wave encounters a material interface, some or all of the wave energy can bounce back into the original medium. The angle of reflection is equal to the angle of incidence, following the law of reflection. Reflection is responsible for phenomena like echoes and the visibility of images in mirrors.
Transmission
Some of the wave energy can pass through the material interface and continue propagating in the new medium. The amount of energy transmitted depends on the properties of the materials involved and the angle of incidence. Transmission is essential for phenomena like light passing through glass or sound traveling through walls.
Absorption:
When waves interact with a material interface, some of the wave energy can be absorbed by the material and converted into other forms of energy, such as heat. The amount of absorption depends on the properties of the materials involved and the frequency of the waves. Absorption plays a role in phenomena like the warming of the Earth’s surface by sunlight or the conversion of sound waves into heat in a room.
In experiments that use rays of light it is best to do these experiments in —————
why?
a dim room
clearly see paths of the rays of light
What is the advantage of using a ray box or laser to produce thin rays of light?
The boundaries between different substances refract light by ——————–
You can investigate this by looking at how much light is ———- when it passes from air into ————- materials
so you can trace the paths of the rays more accurately meaning more exact angle measurements
different amounts
refracted
different
Explain the experiment steps for using transparent materials to investigate refraction:
1) Place a transparent rectangular block on a piece of paper and trace around it. Use a ray box or a laser to shine a ray of light at the middle of one side of the block
2) Trace the incident ray and mark where the light ray emerges on the other side of the block. Remove the block and, with a straight line, join up the incident ray and the emerging point to show the path of the refracted ray through the block
3) Draw the normal at the point where the light ray entered the block. Use a protractor to measure the angle between the incident ray and the normal ( angle of incidence) and the angle between the refracted ray and the normal(the angle of refraction)
4) Repeat this experiment using rectangular blocks made from different materials
You should find that the angle of refraction changes for different materials this difference is due to their
How light reflects depends on the ———- of the surface
optical densities
smoothness
Describe an experiment that allows you to compare how different surfaces reflect light:
1) Take a piece of paper and draw a straight line across it Place an object so one of its sides lines up with this line
2) Shine a ray of light at the object’s surface and trace the incoming and reflected light beams
3) Draw the normal at the point where the ray hits the object. Use a protractor to measure the angle of incidence and the angle of reflection and record these values in a table. Also make a note of the width and brightness of the reflected light ray
4) Repeat the experiment for a range of objects
smooth surfaces like mirrors give ——– reflections where :
Rough surfaces like paper cause —— reflection which cause the reflected beam to be ———————–(or not ———- at all)
The angle of incidence always EQUALS the angle of
clear
the reflected ray is as thin and bright as the incident ray
diffuse
wider and dimmer
observable
reflection
why is it good to repeat experiments:
Having repeated results will make these mistakes :
you could have set up the experiment wrong
or read the wrong number off the protractor
easy to spot
Explain how sound waves travel through the ear
Sound waves that reach the eardrum cause the eardrum to .The vibrations of the eardrum are then transmitted to the tiny bones in the middle ear, known as the ossicles, through thr semi circular canal and to the cochlea which further amplify the vibrations The cochlea turns these vibrations into electrical signals which get sent to your brain and allow you to sense sound
Students should know that the range of normal human hearing is
from
20 Hz to 20 kHz.
Sound waves are caused by :
These vibrations are passed through the surrounding medium as a series of :
sound is a what wave:
sound generally travels faster in solids than in ——- and faster in liquids than in ——-
When a sound wave travels through a solid it does so by:
vibrating objects
compression and rarefactions
longitudinal
liquids
gase
causing the particles to vibrate
what happens to particle sin solid and wave
When a sound wave hits a solid object :
the air particles hitting the object causes the particles in the solid to move back and forth (vibrate) these particles hit the next particles in line and so on passing the sound wave through the object as a series of vibrations
hard flat surfaces will ———- sound waves. Echoes are just—————Sound waves will also refract as they enter —————
As they enter denser material, they ————–. This is because when a wave travels into a different meduim its ——— changes but its ——— remains the same so its ———- must also change
sreflect
reflected sound waves
different media
slow down
wavelength
frequency
speed
Ultra sound is sound with frequencies higher than:
20,000 Hz
How does ultrasound work?
ultra sound waves get partially reflected at boundaries. When a wave passes from one meduim to another some of the wave is reflected off the boundary between the two media, and some is transmitted (and refracted). This is partial reflection.
What this means is that you can point a pulse of ultrasound at an object, and wherever there are boundaries between one substance and another, some of the ultrasound gets reflected back.
The time it takes for the reflections to reach a detector can be used to measure how far away the boundary is.
Ultra sound waves can ————- the body, but whenever they reach a boundary between two different media (like fluid in the womb and skin of the foetus) some of the wave is ——————- and ——————
The exact timing and distribution of these ———– are processed by a computer to produce a video image of the foetus.
No one knows for sure if ultrasound is ———- in all cases
but it is used because ——- would be too dangerous
pass through
reflected back
detected
echoes
safe
x-rays
Ultra sound can also be used to:
and in to image other parts of the body without the risks of radiation
find flaws in objects such as pipes or materials such as wood or metal.
Ultra sound waves entering a material will usually be reflected by the :
however if there is a :
then:
far side of the material
flaw such as a crack inside the object the wave will be reflected sooner
Seismic waves are produced by: P-waves are—————– waves. P-waves travel at different speeds
through —– and ——–. S-waves are ——- seismic waves.
S-waves cannot travel through a ——–. P-waves and S-waves
provide evidence for the :
earthquakes
longitudinal, seismic
solids
liquids
transverse
liquid
structure and size of the Earth’s core.
Echo sounding, using:
is used to
high frequency sound waves
detect objects in deep water and measure water depth.
The waves that form the electromagnetic spectrum are grouped in
terms of their:
Going from :
The groups are:
wavelength and frequency
long to short wavelength (or from low to high frequency) the groups are:
radio, microwave, infrared, visible light (red to violet), ultraviolet, X-rays and gamma rays
Students should be able to give examples that illustrate the transfer
of energy by electromagnetic waves
Sunlight: The Sun emits electromagnetic waves, including visible light, which carries energy to Earth. This energy is essential for photosynthesis in plants and provides warmth on our planet.
Microwave ovens: Microwave ovens use electromagnetic waves in the microwave frequency range to transfer energy to water molecules in food. This causes the molecules to vibrate and generate heat, cooking the food.
Radio waves: Radio waves are used to transfer energy in the form of information from radio stations to radios. The electromagnetic waves carry signals that are converted back into sound waves, allowing us to listen to music or news broadcasts.
Explain how different substances may absorb, transmit, refract or
reflect electromagnetic waves in ways that vary with wavelength.
Absorption: Some materials absorb certain wavelengths of electromagnetic waves while reflecting or transmitting others. For instance, plants absorb visible light for photosynthesis, while materials like glass can absorb and transmit certain wavelengths of light.
Transmission: Transparent materials like glass or water allow certain wavelengths of electromagnetic waves, such as visible light, to pass through with minimal absorption or reflection.
Refraction: When electromagnetic waves pass from one medium to another, such as from air to glass, their speed and direction can change, causing the waves to bend. This phenomenon is known as refraction and is commonly observed when light passes through lenses.
Reflection: Surfaces can reflect electromagnetic waves, bouncing them off in different directions. For example, mirrors reflect visible light, while metals can reflect radio waves.
Convex Lens Ray Diagrams instructions
- Start by drawing a ray going from the top of the object through the centre of the lens. This ray will continue to travel in a straight line
2.Next draw a ray going from the top of the object, travelling parallel to the axis to the lens. When this ray emerges from the lens it will travel directly through the principal focus f - The image is the line drawn from the axis to the point where the above two rays meet
If the object is placed closer to the lens than the ————then a virtual image will be formed and the converging lens ray diagram will be drawn in the following way:
Focal point
you use the normal method but continue the lines backwards that is where the lines will cross
Investigating Emission required practical steps give an example of how to manage risk
1) Place an empty Leslie cube on a heat proof mat
2) Boil water in a kettle and fill the Leslie cube with boiling tube
3) Wait for the cube to warm up, then hold a thermometer against each of the four vertical faces of the cube. You should find that all four faces are the same temperature
4) Hold an infared detector a set distance (e.g 10cm) away from one of the cube’s vertical faces, and record the amount of IR radiation it detects
5) Repeat this measurement for each of the cube’s vertical faces. Make sure you position the detector at the same distance from the cube each time.
6) You should find that you detect more infrared radiation from the black surface than the white one, and more from the matt surfaces than the shiny ones
7) As always you should do this experiment more than once, to make sure your results are repeatable
8) It’s important to be careful when you’re doing this experiment. Don’t try to move the cube when it’s full of boiling water- you might burn your hands. And take care if you’re carrying a full kettle too
Manage risk: make sure your equipment has cooled down properly before handling it and be careful when pouring hot water.
A real image is formed when
light rays converge (come together) at a
point. It can be projected onto a screen because the light actually
passes through the image location.
A virtual image is formed when
light rays appear to diverge (spread
out) but appear to come from a specific point. It cannot be projected
onto a screen because the light doesn’t actually come from the image
location. It uses virtual rays which are shown as dotted lines.
Radio waves can be produced by
oscillation in electrical circuits
When radio waves are absorbed they may create an alternating current with the same ———————-as the radio wave itself,so radio waves can themselves induce :
frequency
oscillations in an electrical
circuit.
Ultraviolet waves, X-rays and gamma rays can have——–
effects on human body tissue. The effects depend on the type of:
. Radiation dose (in ——-) is a
measure of the risk of harm resulting from an exposure of the body
to the radiation
hazardous
radiation and the size of the dose
sieverts
1000 millisieverts (mSv) =
1 sievert
Ultraviolet waves can cause:
. X-rays and gamma rays are ———-
radiation that can cause the:
skin to age prematurely and increase
the risk of skin cancer
ionising
mutation of genes and cancer.
Electromagnetic waves have many practical applications. For example:
* radio waves –
and long wave radio waves
* microwaves –
* infrared –
* visible light –
* ultraviolet –
* X-rays and gamma rays –
give brief explanations why
explain why each type of electromagnetic wave is suitable for the practical
application.
- radio waves – television and radio
wavelengths longer than about 10cm
long-wave radio waves\;
(wave-lengths of 1-10km) can be transmitted across the world as long wavelengths bend around curve of earth.
short-wave radio signals (wavelengths of about 10m-100m) can be received at long distances as they are reflected from the ionsphere
bluetooth- uses short wave radio waves to send data over short distances
meduim wave signals can also reflect from ionsphere depending on atmos conditions at time of day
microwaves – satellite communications, cooking food
Satellite TV: signal from transmitter transmitted into space picked up by satellite receiver dish. Satellite transmits signal back to earth in a different direction. Where it is received by a satellite dish on the ground.
cooking food- microwaves penetrate a few cm into food before being absorbed and transferring energy to water molecules in food causing food to heat up. The water molecules then transfer this energy
- infrared – IF cameras can be used to detect infrared radiation and monitor temperature the camera detects the IR radiation and turns it into an electrical signal
which is displaced on screen as a picture. The hotter an object is the brighter it appears
Food can be cooked using IR radiation temp of food increases when it absorbs IR radiation
electric heaters heat a room in the same way and contain a long piece of wire that heats up when a current flows through it. The wire then emits lots of infrared radiation this is absorbed by objects in the room and energy transferred by ir waves to their thermal energy stores and temp increases - visible light – fibre optic cables thin glass or plastic fibres can carry data over long distances as pulses of visible light, work because of reflection light rays are bounced back and forth until they reach the end of the fibre. Light is not easily absorbed or scattered as it travels along a finre
- ultraviolet – energy efficient lamps, sun tanning- tan beds
fluorescent lights generate UV radiation which is absorbed and re-emitted as visible light by a layer of phosphorus on the inside of the bulb. They’re energy efficient - X-rays and gamma rays – medical imaging and treatments.
X-rays pass easily through flesh but no so easily through denser material like bones its amount of radiation absorbed that gives x-ray image
can be used to treat cancer as high doses of these rays kill all living cells
x-rays and gamma rays harmful so radiographers wear lead aprons and stand behind a lead screen or leave room
A lens forms an image by————– In a convex lens,——————————————————————————————————————. The
distance from the lens to the principal focus is called the ———–. Ray diagrams are used to show the formation of images by ————————————
refracting light.
parallel rays of light are brought to a focus at the principal focus
focal length
convex and concave lenses.
The image produced by a convex lens can be —————–
The image produced by a concave lens is always ——-
either real or virtual
virtual
Each colour within the visible light spectrum has its own
narrow
band of wavelength and frequency
Reflection from a smooth surface in a single direction is called ———- reflection. Reflection from a rough surface causes ———- this is called ——— reflection.
specular
scattering
diffuse
Colour filters work by
absorbing certain wavelengths (and colour)
and transmitting other wavelengths (and colour).
The colour of an opaque object is determined by which :
Wavelengths that are not reflected are ———-. If all wavelengths are reflected equally the
object appears ——–. If all wavelengths are absorbed the objects
appears ———
wavelengths of light are more strongly reflected
absorbed
white
black
Objects that transmit light are either
transparent or translucent.
opaque objects are objects that :
do not transmit light
the colour of opaque objects depends on:
which wavelengths of light are most strongly reflected
for opaque objects that aren’t a primary colour they may be:
reflecting either the wavelengths of light corresponding to that colour or the wavelengths of the primary colours that mix together to make that colour
colour filters are transparent objects that
absorb most wavelengths of light and just let some through
colours filters are used to
filter out different wavelengths of light so that only certain colours are transmitted the rest are absorbed
All bodies (objects), no matter what temperature, emit and absorb —————. The ——- the body, the more ————- it
radiates in a given time.
infrared radiation
hotter
infrared radiation
A perfect black body is an object that :
. A black body does not —— or ——– any
radiation. Since a good absorber is also a————— a perfect
a black body would be the best possible—–.
absorbs all of the radiation incident on it
reflect
transmit
good emitter,
emitter.
- that all bodies (objects) emit:
that the intensity and wavelength distribution of any emission depends on the:
radiation
temp of the body
A body at constant temperature is ———– radiation at the same rate as it is emitting radiation. The temperature of a body
———- when the body absorbs radiation faster than it emits
radiation.
absorbing
increases
The temperature of the Earth depends on many factors
including:
the rates of absorption and emission of radiation,
reflection of radiation into space
1 MHz =
0.000001 Hz
Describe what happens in the electrical circuit when the car aerial absorbs radio waves
ac current is induced in the electrical circuit
Give two ways in which radio waves are different to sound waves
transverse
travel at a higher speed
don’t need a meduim
a red filter is placed in front of a spotlight the spotlight is directed at a blue object
Explain why the blue object appears black
(3 marker)
only red is transmitted by the filter
red is absorbed by the object
no light is reflected by the object
how to calculate the uncertainty
calculate the mean
take away the mean from the highest result
A pupil investigates the properties of sound.
Describe
what they will discover about how sound travels.
Sound is a longitudinal wave (1)
Sound travels better through solids (1)
Sound occurs due to particles vibrating (1)
Sound waves have compressions (1)
Sound waves have rarefactions (1)
Sound waves need a medium to travel through, they can not travel in a vacuum (1)
Any other reasonable answer (1)
describe how the image formed by an eye is different to the image formed in a mirror
The image formed by an eye is:
Real; [1 mark]
Inverted / upside down; [1 mark]
OR
The image formed in a mirror is:
Virtual; [1 mark]
Upright; [1 mark]
[Total: 2 marks]
what two factors determine the focal length of a lens:
Any two from:
The refractive index of the lens
The material of which the lens is made from
Curvature / radius of curvature of the sides
Shape of the lens
describe a method that a student could follow to find out angles of refraction and incidence
* place a glass block on a piece of paper
* draw around the glass block
* use the ray box to shine a ray of light through the glass block
* mark the ray of light entering the glass block
* mark the ray of light emerging from the glass block
* join the points to show the path of the complete ray through the block
* and draw a normal line at 90 degrees to the surface
* use a protractor to measure the angle of incidence
* use a protractor to measure the angle of refraction
* use a ray box to shine a ray of light at a range of different angles (of incidence)
* increase the angle of incidence in 10 degree intervals
* from an angle of incidence of 10 degrees to an angle of incidence of 70
degrees.
going from radio waves to gamma in the EM spectrum the frequency ———– and the wave speed in air ————–
increases
stays the same
Explain how a moving-coil microphone works
sound (waves) cause the diaphragm to vibrate
diaphragm moves is insufficient
1
the diaphragm causes the coil / wire to vibrate
do not accept moves the coil / wire up and down
if m.p.1 and m.p.2 do not score, allow sound (waves)
cause the coil / wire to vibrate for 1 mark
1
the coil / wire moves through the magnetic field
or
the coil / wire cuts magnetic field lines
1
a potential difference is induced (across the ends of the coil / wire)
explain how the properties of x-rays make them suitable for the medical imaging of bones
(2 marker)
(b) pass through soft tissue
allow penetrate for pass through
allow skin/muscle/etc… for soft tissue
pass through tissue is insufficient
1
(but) absorbed by bone
allow do not pass through bone
do not accept reflected by bone
explain why using a wide ray would give less accurate results than using a narrower ray:
it is harder to judge where the centre of a wider ray is
1
causing a larger uncertainty (in the measurements)
allow increasing random errors (in the measurement
What are the advantages of taking more measurements in a experiment :
to reduce the effect of random errors
Explain how the teacher could determine the speed of wave without measuring the frequency
measure the distance travelled by a wave using a metre rule
allow measure the length of the (ripple) tank using a
metre rule
1
measure the time taken (for the wave to travel the measured distance) with a timer /
stopwatch
1
divide the distance by the time
dependant on scoring the first two mark points
A convex lens bulges outwards and causes
it causes rays of light parallel to the axis to be brought together at the principal focus
A concave lens caves inwards
it causes rays of light parallel to axis to spread out
Axis is the
line passing through the middle of the lens
the principal focus of a concave lens is the point where rays hitting the
lens parallel to the axis appear to all come from you can trace them back until they all appear to meet up at a point behind the lens
the principal focus of a concave lens is the point where
the rays hitting the lens parallel to the axis appear to meet up at a point behind the lens
To describe an image you have to say 3 things
how big it is compared to the object
upright or inverted
real or virtual
magnifying glasses use of convex lens:
object being magnified must be closer to the lens than the focal point
red has higher wavelength than violet true or false
true
all different colours of light mixed together creates:
and —- objects reflect all of the wavelengths of visible light ——–
white light
equally
page 148 practical
in a camera a —— lens is used to produce an image of an object on a ——
the image is —– the object
the image is —————– the lens, compared to the distance of the object from the lens
converging
film
smaller than
nearer to
echoes are just
reflected sound waves
p-waves travel ———- than s-waves
faster
