Physics Waves Topic

Question 1

Waves may be either

The ripples on a water surface are an example of a

Answer 1

transverse or longitudinal.

transverse
wave.

Question 2

Longitudinal waves show areas of:
Sound waves travelling through air are

Answer 2

compression and rarefaction.
longitudinal.

Question 3

describe the difference between
longitudinal and transverse waves.

Answer 3

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.

Question 4

Amplitude of a wave:

Answer 4

the maximum displacement of a point on the wave from its undisturbed postion

Question 5

The wavelength:

Answer 5

is the distance from a point on one wave
to the equivalent point on the adjacent wave

Question 6

a period

Answer 6

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. .

Question 7

Frequency

Answer 7

the number of waves passing a point
each second.

Question 8

Period equation
frequency in

Answer 8

1/frequency
hertz

Question 9

The wave speed is

Answer 9

the speed at which the energy is transferred (or
the wave moves) through the medium.

Question 10

wave speed equation with units of measurement

Answer 10

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

Question 11

• describe a method to measure the speed of sound waves in
  air

Answer 11

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)

Question 12

describe a method to measure the speed of ripples on a water
surface.

Answer 12

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

Question 13

Waves can be reflected at the

Answer 13

boundary between two different materials

Question 14

Waves can be absorbed or

Answer 14

transmitted at the boundary between two different materials

Question 15

Reflection

Answer 15

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.

Question 16

Transmission

Answer 16

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.

Question 17

Absorption:

Answer 17

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.

Question 18

In experiments that use rays of light it is best to do these experiments in —————
why?

Answer 18

a dim room
clearly see paths of the rays of light

Question 19

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

Answer 19

so you can trace the paths of the rays more accurately meaning more exact angle measurements

different amounts
refracted
different

Question 20

Explain the experiment steps for using transparent materials to investigate refraction:

Answer 20

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

Question 21

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

Answer 21

optical densities

smoothness

Question 22

Describe an experiment that allows you to compare how different surfaces reflect light:

Answer 22

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

Question 23

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

Answer 23

clear
the reflected ray is as thin and bright as the incident ray
diffuse
wider and dimmer
observable

reflection

Question 24

why is it good to repeat experiments:

Having repeated results will make these mistakes :

Answer 24

you could have set up the experiment wrong
or read the wrong number off the protractor

easy to spot

Question 25

Explain how sound waves travel through the ear

Answer 25

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

Question 26

Students should know that the range of normal human hearing is from

Answer 26

20 Hz to 20 kHz.

Question 27

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:

Answer 27

vibrating objects compression and rarefactions longitudinal liquids gase causing the particles to vibrate

Question 28

# what happens to particle sin solid and wave When a sound wave hits a solid object :

Answer 28

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

Question 29

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

Answer 29

sreflect reflected sound waves different media slow down wavelength frequency speed

Question 30

Ultra sound is sound with frequencies higher than:

Answer 30

20,000 Hz

Question 31

How does ultrasound work?

Answer 31

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.

Question 32

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

Answer 32

pass through reflected back detected echoes safe x-rays

Question 33

Ultra sound can also be used to: and in to image other parts of the body without the risks of radiation

Answer 33

find flaws in objects such as pipes or materials such as wood or metal.

Question 34

Ultra sound waves entering a material will usually be reflected by the : however if there is a : then:

Answer 34

far side of the material flaw such as a crack inside the object the wave will be reflected sooner

Question 35

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 :

Answer 35

earthquakes longitudinal, seismic solids liquids transverse liquid structure and size of the Earth’s core.

Question 36

Echo sounding, using: is used to

Answer 36

high frequency sound waves detect objects in deep water and measure water depth.

Question 37

The waves that form the electromagnetic spectrum are grouped in terms of their: Going from : The groups are:

Answer 37

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

Question 38

Convex Lens Ray Diagrams instructions

Answer 38

1. 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 3. The image is the line drawn from the axis to the point where the above two rays meet

Question 39

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:

Answer 39

Focal point you use the normal method but continue the lines backwards that is where the lines will cross

Question 40

Investigating Emission required practical steps give an example of how to manage risk

Answer 40

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.

Question 41

A real image is formed when it can be projected : because:

Answer 41

light rays converge (come together) at a point. It can be projected onto a screen because the light actually passes through the image location.

Question 42

A virtual image is formed when

Answer 42

when the rays are diverging so the light from the ibject appears to be coming from a completley different place

Question 43

Radio waves can be produced by

Answer 43

oscillation in electrical circuits

Question 44

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 :

Answer 44

frequency oscillations in an electrical circuit.

Question 45

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

Answer 45

hazardous radiation and the size of the dose sieverts

Question 46

1000 millisieverts (mSv) =

Answer 46

1 sievert

Question 47

Ultraviolet waves can cause: . X-rays and gamma rays are ---------- radiation that can cause the:

Answer 47

skin to age prematurely and increase the risk of skin cancer ionising mutation of genes and cancer.

Question 48

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.

Answer 48

* 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

Question 49

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 ------------------------------------

Answer 49

refracting light. parallel rays of light are brought to a focus at the principal focus focal length convex and concave lenses.

Question 50

The image produced by a convex lens can be ----------------- The image produced by a concave lens is always -------

Answer 50

either real or virtual virtual

Question 51

Each colour within the visible light spectrum has its own

Answer 51

narrow band of wavelength and frequency

Question 52

Reflection from a smooth surface in a single direction is called ---------- reflection. Reflection from a rough surface causes ---------- this is called --------- reflection.

Answer 52

specular scattering diffuse

Question 53

# 2 marks Colour filters work by

Answer 53

absorbing certain wavelengths (and colour) and transmitting other wavelengths (and colour).

Question 54

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 ---------

Answer 54

wavelengths of light are more strongly reflected absorbed white black

Question 55

Objects that transmit light are either

Answer 55

transparent or translucent.

Question 56

opaque objects are objects that :

Answer 56

do not transmit light

Question 57

the colour of opaque objects depends on:

Answer 57

which wavelengths of light are most strongly reflected

Question 58

for opaque objects that aren't a primary colour they may be:

Answer 58

reflecting either the wavelengths of light corresponding to that colour or the wavelengths of the primary colours that mix together to make that colour

Question 59

colour filters are transparent objects that

Answer 59

absorb most wavelengths of light and just let some through

Question 60

colours filters are used to

Answer 60

filter out different wavelengths of light so that only certain colours are transmitted the rest are absorbed

Question 61

All bodies (objects), no matter what temperature, emit and absorb ---------------. The ------- the body, the more ------------- it radiates in a given time.

Answer 61

infrared radiation hotter infrared radiation

Question 62

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-----.

Answer 62

absorbs all of the radiation incident on it reflect transmit good emitter, emitter.

Question 63

* that all bodies (objects) emit: that the intensity and wavelength distribution of any emission depends on the:

Answer 63

radiation temp of the body

Question 64

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.

Answer 64

absorbing increases

Question 65

The temperature of the Earth depends on many factors including:

Answer 65

the rates of absorption and emission of radiation, reflection of radiation into space

Question 66

1 MHz =

Answer 66

0.000001 Hz

Question 67

Describe what happens in the electrical circuit when the car aerial absorbs radio waves

Answer 67

ac current is induced in the electrical circuit

Question 68

Give two ways in which radio waves are different to sound waves

Answer 68

transverse travel at a higher speed don't need a meduim

Question 69

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)

Answer 69

only red is transmitted by the filter red is absorbed by the object no light is reflected by the object

Question 70

how to calculate the uncertainty

Answer 70

calculate the mean take away the mean from the highest result

Question 71

A pupil investigates the properties of sound. Describe what they will discover about how sound travels.

Answer 71

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)

Question 72

describe how the image formed by an eye is different to the image formed in a mirror

Answer 72

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]

Question 73

what two factors determine the focal length of a lens:

Answer 73

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

Question 74

describe a method that a student could follow to find out angles of refraction and incidence

Answer 74

*   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.

Question 75

going from radio waves to gamma in the EM spectrum the frequency ----------- and the wave speed in air --------------

Answer 75

increases stays the same

Question 76

Explain how a moving-coil microphone works

Answer 76

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)

Question 77

explain how the properties of x-rays make them suitable for the medical imaging of bones (2 marker)

Answer 77

(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

Question 78

explain why using a wide ray would give less accurate results than using a narrower ray:

Answer 78

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

Question 79

What are the advantages of taking more measurements in a experiment :

Answer 79

to reduce the effect of random errors

Question 80

Explain how the teacher could determine the speed of wave without measuring the frequency

Answer 80

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

Question 81

A convex lens bulges outwards and causes

Answer 81

it causes rays of light parallel to the axis to be brought together at the principal focus

Question 82

A concave lens caves inwards

Answer 82

it causes rays of light parallel to axis to spread out

Question 83

Axis is the

Answer 83

line passing through the middle of the lens

Question 84

the principal focus of a concave lens is the point where rays hitting the

Answer 84

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

Question 85

the principal focus of a concave lens is the point where

Answer 85

the rays hitting the lens parallel to the axis appear to meet up at a point behind the lens

Question 86

To describe an image you have to say 3 things

Answer 86

how big it is compared to the object upright or inverted real or virtual

Question 87

magnifying glasses use of convex lens:

Answer 87

object being magnified must be closer to the lens than the focal point

Question 88

red has higher wavelength than violet true or false

Answer 88

true

Question 89

all different colours of light mixed together creates: and ---- objects reflect all of the wavelengths of visible light --------

Answer 89

white light equally

Question 91

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

Answer 91

converging film smaller than nearer to

Question 92

echoes are just

Answer 92

reflected sound waves

Question 93

p-waves travel ---------- than s-waves

Answer 93

faster

Question 94

increasing amp increases also go over ray diagrams

Answer 94

loudness

Question 95

how to work out if an image is virtual from a ray diagram

Answer 95

it will be on the same side of the lens as the original object