IGCSE Physics 0625 — Topic 3: Waves — Paper 2 (MCQ) Cambridge Challenge 2

Question 1

Water waves on a pond and sound waves in air are compared.

Which row is correct?

AWater surface waves: longitudinal, the surface moves along the direction of travel. Sound: transverse, air particles vibrate at right angles to the wave’s travel BBoth are transverse waves, because all waves make the material they travel through vibrate at right angles to the direction the wave moves in CWater surface waves: transverse, the surface moves at right angles to the wave’s travel. Sound: longitudinal, air particles vibrate along the direction of travel DBoth are longitudinal waves, because every wave that needs a substance to travel through must make its particles vibrate along the direction of motion

Question 2

A wave is drawn on a displacement-distance graph. The vertical distance from the top of a crest to the bottom of the neighbouring trough is 0.040 m.

What is the amplitude of the wave?

A0.080 m B0.020 m C0.010 m D0.040 m

Question 3

Ripples on a lake have a wavelength of 0.60 m and a frequency of 2.5 Hz.

What is the speed of the ripples?

A1.5 m/s B3.1 m/s C0.24 m/s D4.2 m/s

Question 4

A swimmer watches wave crests pass a fixed buoy. One crest passes every 0.40 s, and the distance between neighbouring crests is 1.2 m.

What is the speed of the waves?

A0.48 m/s B0.33 m/s C3.0 m/s D1.6 m/s

Question 5

A cork floats on a pond as ripples travel steadily past it towards the shore.

What does the cork do, and what does this show about the wave?

AIt drifts slowly against the wave’s direction; the water flows backwards underneath to replace what each wave carries forward BIt remains perfectly still; the ripples travel through the water without disturbing anything that floats upon the surface CIt rides the crest all the way to the shore; the wave carries both its energy and the water along with it as it travels DIt bobs up and down on the spot; the wave transfers energy across the pond without transferring the water itself

Question 6

Water waves travel from deep water straight into a shallower region, crossing the boundary head-on.

Which row shows what happens to their speed, wavelength and frequency?

ASpeed: decreases. Wavelength: increases. Frequency: increases BSpeed: decreases. Wavelength: decreases. Frequency: unchanged CSpeed: decreases. Wavelength: unchanged. Frequency: decreases DSpeed: unchanged. Wavelength: decreases. Frequency: increases

Question 7

Plane water waves pass through a gap in a harbour wall and spread out into the water beyond.

Which change would make this spreading (diffraction) MORE pronounced?

AMaking the gap wider, so that a greater number of the incoming wavefronts are able to pass through it BIncreasing the frequency of the waves, so that they carry more energy through the gap and spread further CMaking the waves travel faster before the gap, so that they burst through with more forward momentum DMaking the gap narrower, so that its width becomes closer to the wavelength of the waves

Question 8

Plane wavefronts in a ripple tank strike a straight barrier and are reflected.

Which statement about the reflected waves is correct?

AThey leave the barrier so that the angle of reflection equals the angle of incidence, and their wavelength is unchanged BThey travel back along exactly the path they arrived on, whatever the angle at which they struck the barrier CThey pass mostly through the barrier, and only the small reflected part keeps the original wavelength of the waves DThey leave the barrier at a smaller angle than they arrived, and their wavelength is reduced by the reflection

Question 9

When waves cross from one medium into another, their frequency stays the same even though their speed and wavelength change.

Why must the frequency stay the same?

AFrequency and speed are the same quantity expressed in different units, so a change in one is automatically a change in the other BWaves arrive at the boundary at a rate set by the source, and each wave that arrives must continue into the new medium at that same rate CThe frequency is locked to the wavelength, and since the wavelength belongs to the wave itself, neither is able to change anywhere DThe new medium always adjusts its own natural frequency until it exactly matches the frequency of the waves that are arriving

Question 10

A microwave oven uses electromagnetic waves of wavelength 0.030 m, travelling at 3.0 × 10⁸ m/s.

What is their frequency?

A1.0 × 10¹⁰ Hz B9.0 × 10⁶ Hz C1.0 × 10⁷ Hz D3.0 × 10⁹ Hz

Question 11

A student stands 0.80 m in front of a plane mirror.

Which statement about her image is correct?

AIt is virtual, slightly smaller than her, 1.6 m behind the mirror, with top and bottom appearing swapped BIt is real, the same size as her, 0.80 m behind the mirror, and it could be captured on a screen placed there CIt is virtual, the same size as her, 0.80 m behind the mirror, with left and right appearing swapped DIt is real, the same size as her, formed on the surface of the mirror itself, with left and right appearing swapped

Question 12

A simple periscope contains two parallel plane mirrors, each fixed at 45° to the vertical tube.

How does it allow a user at the bottom to see over a wall?

AThe mirrors store the image at the top of the tube, and the stored picture is carried down the tube by the air inside it to the user BLight from the scene is reflected through 90° at the top mirror, travels down the tube, and is reflected through 90° again into the user’s eye CThe top mirror bends the light by refraction as it passes through the glass, steering the rays down the tube towards the user’s eye below DEach mirror magnifies the scene slightly, and the two magnifications together bring the distant view close enough for the user to see it

Question 13

A ray of light passes from air into a glass block, striking the surface at an angle to the normal.

Which row describes what happens as the ray enters the glass?

AIt slows down and bends away from the normal; its frequency decreases with the speed BIt speeds up and bends towards the normal; its frequency increases inside the glass CIt keeps the same speed but bends towards the normal; only its direction is changed by the glass DIt slows down and bends towards the normal; its frequency stays the same

Question 14

A ray of light in air strikes a transparent plastic block at an angle of incidence of 45°. The angle of refraction inside the plastic is 28°.

What is the refractive index of the plastic?

A1.6 B2.5 C1.5 D0.66

Question 15

The refractive index of a glass is 1.5. The speed of light in air is 3.0 × 10⁸ m/s.

What is the speed of light in the glass?

A2.0 × 10⁸ m/s B3.0 × 10⁸ m/s C4.5 × 10⁸ m/s D1.5 × 10⁸ m/s

Question 16

Light travels inside a plastic of refractive index 1.4 towards a boundary with air.

What is the critical angle of the plastic?

A36° B46° C44° D72°

Question 17

Light can undergo total internal reflection at a boundary.

Which TWO conditions must BOTH be met?

AThe light must strike the boundary at exactly the critical angle, and the two media must have exactly equal refractive indices BThe light must be travelling in the denser medium towards the less dense one, and must strike the boundary at less than the critical angle CThe light must be travelling in the less dense medium towards the denser one, and must strike the boundary at more than the critical angle DThe light must be travelling in the denser medium towards the less dense one, and must strike the boundary at more than the critical angle

Question 18

An object is placed well beyond twice the focal length of a converging lens.

Which row describes the image formed?

AReal, inverted, larger than the object, formed on the far side of the lens between the lens and its focal point BVirtual, upright, larger than the object, formed on the same side of the lens as the object itself CReal, inverted, smaller than the object, formed on the far side of the lens between F and 2F DReal, upright, smaller than the object, formed on the far side of the lens beyond twice the focal length

Question 19

A slide projector must throw a greatly enlarged image of a small slide onto a distant screen.

Where must the slide be placed relative to the projector’s converging lens, and what will the image be like?

ACloser to the lens than one focal length; the image on the screen is virtual, upright and magnified, so the slide is loaded the right way up BBetween one and two focal lengths from the lens; the image on the screen is real, inverted and magnified, so the slide is loaded upside-down CBeyond twice the focal length from the lens; the image on the screen is real, upright and smaller, so the slide must be loaded upside-down DExactly at the focal point of the lens; the image forms at infinity, which is what allows any screen at any distance to receive it sharply

Question 20

A narrow beam of white light enters a glass prism and a spectrum of colours emerges.

Why does the prism separate the colours?

AEach colour travels at a slightly different speed in glass, so each is refracted through a slightly different angle, violet being deviated the most BEach colour travels at a different speed in the air after leaving the prism, and the faster colours pull ahead to form the top of the spectrum CThe glass absorbs white light completely and then re-emits it as seven separate colours, in the order of the energy that each one carries DThe prism adds the colours to the white light as it passes through, with each face of the glass prism contributing its own band of colour

Question 21

Which list shows electromagnetic radiations in order of INCREASING frequency?

ARadio waves → infrared → visible light → ultraviolet → X-rays BInfrared → radio waves → visible light → X-rays → ultraviolet CX-rays → ultraviolet → visible light → infrared → radio waves DRadio waves → ultraviolet → visible light → infrared → X-rays

Question 22

Communication with satellites in orbit generally uses microwaves rather than lower-frequency radio waves.

Why are microwaves suitable for the satellite link?

AThey travel through the vacuum of space faster than radio waves do, which shortens the delay on every satellite connection BThey are the only electromagnetic waves that are able to leave the Earth’s atmosphere without being pulled back by gravity CThey pass through the atmosphere and ionosphere with little absorption or reflection, so they can travel between the ground and the satellite DThey can be received without any aerial or dish, which makes the ground equipment for a satellite link far simpler to build

Question 23

Which row correctly matches each radiation to one of its everyday uses?

AInfrared: medical images of broken bones. Ultraviolet: mobile phone signals. Microwaves: television remote controls BInfrared: mobile phone signals. Ultraviolet: medical images of broken bones. Microwaves: detecting forged banknotes CInfrared: television remote controls. Ultraviolet: detecting forged banknotes. Microwaves: mobile phone signals DInfrared: detecting forged banknotes. Ultraviolet: television remote controls. Microwaves: medical images of broken bones

Question 24

Which row correctly pairs a radiation with the harm over-exposure to it can cause?

AUltraviolet: damage to skin cells and eyes, raising the risk of skin cancer. Gamma rays: damage to cells deep in the body through their ionising effect BUltraviolet: damage only to people who wear glasses. Gamma rays: dangerous only when their loud sound is heard at close range CUltraviolet: internal heating of the body’s water. Gamma rays: sunburn and damage to the surface of the skin only DUltraviolet: no harm at any exposure, because it arrives naturally from the Sun. Gamma rays: harmless because they pass straight through the body

Question 25

A long-wave radio transmitter broadcasts at a frequency of 200 kHz. Radio waves travel at 3.0 × 10⁸ m/s.

What is the wavelength of the broadcast?

A670 m B6.7 × 10⁻⁴ m C1500 m D60 000 m

Question 26

In a vacuum, the speed of gamma rays is compared with the speed of radio waves.

Which statement is correct?

ARadio waves travel faster, because their much longer wavelength lets them cover more distance in each cycle BNeither can travel at all, because a vacuum contains no particles for any wave to make its way through CThey travel at exactly the same speed, because all electromagnetic waves in a vacuum travel at 3.0 × 10⁸ m/s DGamma rays travel faster, because waves that carry more energy always move more quickly through empty space

Question 27

A telephone signal can be sent along a cable either as an analogue signal or as a digital signal. Over a long distance the signal weakens and picks up random noise, and must be boosted at intervals.

Why does the digital transmission arrive with higher quality?

ABoosting an analogue signal removes its noise but also removes part of the speech, while digital boosting simply makes the whole signal louder BA digital signal is immune to noise while it travels, because interference of every kind affects only the older analogue kind of cable CA digital signal travels along the cable very much faster than an analogue one, arriving before any noise has enough time to attach itself DA digital signal has only two levels, so each booster can tell signal from noise and regenerate a clean, exact copy — noise is stripped out at every stage

Question 28

A radio signal is sent from a ground station to a satellite 3.6 × 10⁷ m above the Earth, and the reply returns immediately.

What is the minimum delay between sending and receiving, with radio waves travelling at 3.0 × 10⁸ m/s?

A0.12 s B0.24 s C8.3 s D2.4 s

Question 29

A guitar string is plucked and a note is heard across the room.

Which sequence correctly describes how the sound reaches a listener?

AThe string pushes a single pulse of moving air across the room, and this wind arrives at the ear carrying the note along with it BThe vibration travels along the surfaces of the room’s walls and floor, and the listener hears whatever reaches the ground beneath them CThe vibrating string makes the air next to it vibrate, and the vibrations travel through the air as compressions and rarefactions to the listener’s ear DThe vibrating string releases a stream of sound particles, which fly across the room in straight lines until they strike the listener’s ear

Question 30

An electric bell rings inside a sealed glass jar. As the air is gradually pumped out, the sound fades away to almost nothing — yet the hammer can still be seen striking the bell.

What does this experiment demonstrate?

ASound needs a medium such as air to travel through, while light can travel through a vacuum BRemoving the air stops the bell’s hammer from vibrating properly, which is the real reason the ringing sound dies away CSound needs a medium such as air to travel through, and light also needs air, but light needs far less of it to be seen clearly DThe pump removes the sound from the jar along with the air, storing both of them until the jar is refilled again later

Question 31

As a sound wave travels through air, it consists of compressions and rarefactions.

What is a compression?

AA region where the air particles are momentarily closer together than normal, giving a slightly higher pressure BA region where the air particles are momentarily further apart than normal, giving a slightly lower pressure CA group of air particles that travels with the wave all the way from the source to the listener’s ear DA region where the air particles have stopped moving completely while the rest of the wave passes by them

Question 32

The speed of sound is compared in steel, in water and in air.

Which ranking is correct, and why?

AThe same speed in all three, because the speed of sound is a fixed constant that belongs to the sound and not to the material BFastest in water, slower in steel, slowest in air — liquids combine the free movement of gases with the close packing of solids CFastest in air, slower in water, slowest in steel — the emptier the material, the less there is to slow the travelling sound down DFastest in steel, slower in water, slowest in air — the closer together the particles, the more rapidly the vibrations are passed on

Question 33

A hearing test shows that a healthy young person can hear sounds across the normal human range.

What is that range, and what is sound above it called?

AAbout 1 Hz to 1 000 000 Hz; there is no special name for any sound outside it BAbout 20 Hz to 20 000 Hz; sound above the range is called infrasound CAbout 20 000 Hz to 40 000 Hz; sound below this range is called ultrasound DAbout 20 Hz to 20 000 Hz; sound above the range is called ultrasound

Question 34

A hiker shouts towards a cliff and hears the echo 1.5 s later. The speed of sound in air is 340 m/s.

How far away is the cliff?

A510 m B255 m C227 m D170 m

Question 35

Two sounds are displayed one after the other on the same oscilloscope with unchanged settings. The second trace has more waves across the screen and a smaller height than the first.

How does the second sound compare with the first?

AIt is higher in pitch and louder: both the number of waves on the screen and the height of the trace measure the loudness of a sound BIt is the same pitch but quieter: the number of waves on a screen depends only on the oscilloscope and never on the sound itself CIt is lower in pitch and louder: more waves across the screen means each wave is weaker, and the smaller height means the sound is nearer DIt is higher in pitch and quieter: more waves across the screen means higher frequency, and smaller height means smaller amplitude

Question 36

To measure the speed of sound, student A stands 500 m from student B in an open field. A bangs two cymbals together; B sees the flash of the cymbals meeting and starts a stopwatch, stopping it on hearing the bang 1.47 s later.

Why is this method valid, and what speed does it give?

ALight travels at only twice the speed of sound in air, so half of the measured time must first be subtracted before the speed can be worked out BThe light from the cymbals arrives almost instantly, so the timed delay is essentially all due to the sound: v = 500 / 1.47 ≈ 340 m/s CThe light and the sound leave the cymbals at the same moment and travel at the same speed, so either one of them could have been timed: v ≈ 340 m/s DThe stopwatch measures how long the cymbals vibrate for after being struck, and the speed is the distance divided by that vibration time: v ≈ 340 m/s

Question 37

Engineers test a solid metal railway axle for hidden internal cracks without cutting it open, using ultrasound.

How does the test work?

AThe ultrasound heats any cracked region of the metal more than the solid parts, and a thermal camera then photographs the warmed area from outside BUltrasound passes only through cracked metal, so any signal detected on the far side of the axle proves that a hidden crack must be present CThe pulse becomes audible sound inside any crack that it enters, and an engineer listening at the surface hears ringing wherever a flaw exists DA pulse sent into the metal reflects from any internal crack as well as from the far surface; an unexpected early echo reveals a flaw and its depth

Question 38

During a thunderstorm, a student sees a lightning flash and hears the thunder 4.0 s later. Sound travels at 340 m/s, and the light arrives essentially instantly.

How far away was the lightning strike?

AAbout 680 m BAbout 85 m CAbout 2700 m DAbout 1400 m

Question 39

A tuning fork’s sound is displayed on an oscilloscope. One complete wave takes 2.5 ms.

What is the frequency of the note?

A400 Hz B4000 Hz C2.5 Hz D40 Hz

Question 40

In a sound wave travelling through air at 340 m/s, the distance between one compression and the next is 1.7 m.

What is the frequency of the sound, and can it be heard?

A200 Hz, which cannot be heard because only frequencies above 20 kHz are audible B200 Hz, which is audible because it lies inside the human hearing range C580 Hz, which is audible because it lies inside the human hearing range D0.005 Hz, which cannot be heard because it lies far below the human hearing range

Paper 2 — Multiple Choice

Section A: General Wave Properties

Section B: Light

Section C: The Electromagnetic Spectrum

Section D: Sound