IB Physics Review - Waves & Vibrations - MC

IB PHYSICS HL MULTIPLE CHOICE REVIEW WAVES & VIBRATIONS 1.

A sound emitting source moves along a straight line with speed v relative to an observer at rest. Observer v

The speed of sound relative to the medium is c. The observer measures the speed of sound emitted by the source as A. c. B. c + v. C. c – v. D. v – c. (1)

2.

The diagram below shows ocean waves incident on a stone barrier protecting boats anchored behind it.

Waves Boats Barrier The boats could still be at risk of damage by waves mainly as a result of A. refraction.

B. standing waves.

C. diffraction.

D. reflection. (1)

1 3. Two particles X and Y are situated a distance  apart on a stationary wave of wavelength λ. The variation 2 with time t of the displacement dx of X is shown below. dX

0 0

t

Which one of the following correctly shows the variation with time t of the displacement dY of particle Y? A.

0 0

C.

B.

dY

0 0

0 0

t

D.

dY

t

dY

t

dY

0 0

t

(1) 1

4.

The speed of a wave is defined as A.

the speed at which the particles of the wave vibrate.

B.

the speed of the medium through which the wave passes.

C.

the speed of transfer of the energy of the wave.

D.

the speed at which the vibrations of the wave are produced. (1)

5.

Which diagram best shows diffraction of plane wavefronts at a single slit?

A.

B.

C.

D.

(1)

6.

A source of sound moves directly towards a stationary observer. The frequency of the sound detected by the observer is different from the source frequency because A.

the loudness of the sound increases as the source moves towards the observer.

B.

the apparent wavelength of the sound is longer.

C.

the speed of sound relative to the observer is increased.

D.

the apparent wavelength of the sound is shorter. (1)

2

7.

A pipe, open at both ends, has a length L. The speed of sound in the air in the pipe is v. The frequency of vibration of the fundamental (first harmonic) standing wave that can be set up in the pipe is A.

v . 2L

B.

L . 2v

C.

4v . L

D.

L . 4v (1)

8.

Two lamps producing light of the same colour are placed close to one another. A two source interference pattern is not observed because A.

the lamps do not emit light of a single frequency.

B.

the phase difference between the light from the lamps is continually changing.

C.

the intensity of the light emitted by the lamps is not the same.

D.

the two lamps are not exact point sources. (1)

9.

Standing waves in an open pipe come about as a result of A.

reflection and superposition.

B.

reflection and diffraction.

C.

superposition and diffraction.

D.

reflection and refraction. (1)

10.

A source of sound emits waves of wavelength λ, period T and speed v when at rest. The source moves away from a stationary observer at speed V, relative to the observer. The wavelength of the sound waves, as measured by the observer is A.

λ + vT.

B.

λ – vT.

C.

λ +VT.

D.

λ – VT. (1)

3

11.

Which of the following diagrams best illustrates the diffraction of waves by an obstacle? A.

B.

C.

D.

(1)

12.

A source S produces sound waves of frequency f and is moving along a straight line as shown below.

I

IV

S

II

III

Which observer I, II, III or IV could hear a sound of frequency f when the source is in the position shown? A.

I

B.

II

C.

III

D.

IV (1)

13.

In order that the interference between the waves emitted by two light sources can be observed, it is essential that the sources must emit waves that A.

have the same amplitude.

B.

are in phase.

C.

have the same colour.

D.

have a constant phase difference between them. (1)

4

14.

Graph P shows how the displacement at one point in a wave varies with time. Graph Q shows how the displacement in the same wave varies with distance along the wave at one particular time.

Graph P displacement

0 0

t1

t2

time

Graph Q displacement

0 0

x1

x2

x3

distance

Which one of the following expressions gives the speed of the wave? A.

x1 t1

B.

x2 t2

C.

x 2  x1  t 2  t1 

D.

x3  x1  t 2  t1  (1)

15.

A string is stretched between two fixed points. The string is plucked at its centre and is seen to vibrate with frequency f as shown below.

Which one of the following expressions gives the frequencies of other possible modes of vibration that have an antinode at the centre? The number n in each expression is an integer. A.

nf

B.

(2n – 1)f

C.

(n – 1)f

D.

(n + 1)f (1) 5

16.

Which one of the following diagrams best represents wavefronts produced by a source of sound of constant frequency as it moves at constant speed towards a stationary observer at O? A.

B.

O

C.

O

D.

O

O

(1) 17.

The waves from two light sources meet at a point. Which condition is essential for interference to be observed? A.

Constant phase difference between the waves

B.

Equal amplitude of the waves

C.

Equal frequency of the waves

D.

Equal intensities of the waves (1)

18.

Light from a double slit arrangement produces bright and dark fringes on a screen in the region near point P, as indicated below.

P

coherent light

screen

double slit not to scale

The light from the two slits has equal amplitudes on reaching point P. Which one of the following gives the change, if any, in the appearance of the bright and the dark fringes when the amplitude of the light wave from one slit is reduced? Bright fringes

Dark fringes

A.

Remains the same

Remains the same

B.

Becomes less bright

Remains the same

C.

Becomes less bright

Becomes more bright

D.

Remains the same

Becomes more bright (1) 6

19.

The speed of sound in still air is c. A source of sound moves away from an observer at speed v. What will be the speed of sound as measured by the observer? A. c

B.

c+v

C.

c–v

D.

v–c (1)

20.

For a standing wave, all the particles between two successive nodes have the same A.

amplitude only.

B.

frequency only.

C.

amplitude and frequency.

D.

frequency and energy. (1)

21.

The diagram below shows two pulses on a string travelling toward each other.

Which of the following diagrams best shows the shape of the string after the pulses have passed through each other?

A.

B.

C.

D.

(1)

7

22.

Two identical sources in a ripple tank generate waves of wavelength λ. The interfering waves produce the wave pattern shown below. II III I

IV

Along which of the labelled lines is the path difference between the waves from the sources equal to 1.5 λ? A.

I

B.

II

C.

III

D.

IV (1)

23.

Which one of the following is correct for transfer of energy along a standing wave and for amplitude of vibration of the standing wave? Transfer of energy along a standing wave

Amplitude of vibration of the standing wave

A.

None

Constant amplitude

B.

None

Variable amplitude

C.

Energy is transferred

Constant amplitude

D.

Energy is transferred

Variable amplitude (1)

24.

Two pipes P and Q are of the same length. Pipe P is closed at one end and pipe Q is open at both ends. The fundamental frequency (first harmonic) of the closed pipe P is 220 Hz. The best estimate for the fundamental frequency of the open pipe Q is A.

880 Hz.

B.

440 Hz.

C.

110 Hz.

D.

55 Hz. (1)

8

25.

In order that the light from two sources produces an observable interference pattern, it is necessary that A.

the sources must be point sources.

B.

the light emitted by the sources must be monochromatic.

C.

the light from each source must be of the same intensity.

D.

the light from the sources must be coherent. (1)

26.

Monochromatic light crosses the boundary between two media. Which of the following quantities is always the same for the light in both media? A.

Amplitude

B.

Frequency

C.

Speed

D.

Wavelength (1)

27.

A point source is moving at a constant speed in a straight-line towards the right and emits sound waves of constant frequency. The speed of the source is less than the speed of sound. Which of the diagrams correctly shows the wavefronts emitted by the source?

A.

B.

C.

D.

(1)

9

28.

The diagram below shows the arrangement for a Young’s double slit experiment.

single slit

double slit

S1

monochromatic light source

S

S2

The function of the single slit is A.

to direct the light towards S1 and S2.

B.

to ensure equal intensities of light at S1 and S2.

C.

to produce coherent light at S1 and S2.

D.

to reduce the intensity of light at S1 and S2. (1)

29.

Which one of the following correctly describes the change, if any, in the speed, wavelength and frequency of a light wave as it passes from air into glass? Speed

Wavelength

Frequency

A.

decreases

decreases

unchanged

B.

decreases

unchanged

decreases

C.

unchanged

increases

decreases

D.

increases

increases

unchanged (1)

10

30.

A tube is filled with water and a vibrating tuning fork is held above its open end. tuning fork x y

water tap

The tap at the base of the tube is opened. As the water runs out, the sound is loudest when the water level is a distance x below the top of the tube. A second loud sound is heard when the water level is a distance y below the top. Which one of the following is a correct expression for the wavelength  of the sound produced by the tuning fork? =y

A.

 = 2x

B.

C.

=y−x

D.

 = 2(y − x) (1)

31.

A source S, moving at constant speed, emits a sound of constant frequency. The source passes by a stationary observer O, as shown below.

S

O Which one of the following shows the variation with time t of the frequency f observed at O as the source S approaches and passes by the observer. A.

0

C.

B.

f

0

0

0

t

D.

f

0

t

f

0

t

0

t

f

0

(1)

11

32.

Water waves of wavelength 2.0 m are produced by two sources S1 and S2. The sources vibrate in phase. S1

S2

1m

3m P

Point P is 1 m from S1 and 3 m from S2. S1 alone and S2 alone each produce a wave of amplitude a at P. Which one of the following is the amplitude of the resultant wave at point P when S1 and S2 are both emitting waves? A.

2a

B.

a

C.

1 a 2

D.

Zero (1)

33.

A source of sound is placed near the open end of a cylindrical tube that lies on a horizontal table. The tube has some powder sprinkled along its length. The powder collects in piles along the length of the tube as shown below. d

source of sound

The distance between two consecutive piles of powder is d and the speed of sound in the tube is v. The frequency of the source is A.

v . 2d

B.

v . d

C.

dv.

D.

2dv. (1)

34.

A well-insulated container is divided into two equal volumes by a wall. In one half there is an ideal gas and the other is a vacuum as shown below.

gas

vacuum

gas

The wall is now removed. Which one of the following correctly gives the changes, if any, that take place in the internal energy and entropy of the gas? Internal energy

Entropy

A.

stays the same

stays the same

B.

stays the same

increases

C.

decreases

stays the same

D.

decreases

increases (1) 12

35.

The distance S2N – S1N is equal to c . 2f

A.

c . f

B.

f . 2c

C.

D.

f . c (1)

36.

A stationary source emits sound of frequency f0. An observer is moving towards the source at constant speed along the path indicated by the dotted line. The observer passes very close to the source at time T.

stationary source observer Which one of the following graphs best shows the variation with time t of the frequency f heard by the observer? A.

f

B.

f0

f0

T C.

f

t

f

D.

f0

T

t

T

t

f f0

T

t

(1)

37.

A police car, sounding its siren, is travelling at constant speed towards a stationary observer. The sound emitted by the siren is of constant frequency. The frequency of the sound as heard by the observer is higher than that heard by the driver of the police car. The reason for this is that A.

the wavefronts received by the observer are closer together than the wavefronts received by the driver.

B.

the speed of the wavefronts is greater as measured by the observer than by the driver.

C.

the speed of the wavefronts is less as measured by the observer than by the driver.

D.

the wavefronts received by the observer are further apart than the wavefronts received by the driver. (1)

38.

The light waves emitted by two coherent sources overlap and form an observable interference pattern. The word coherent in this situation means that A.

the sources are point sources.

B.

there is a constant phase difference between the light waves emitted by the sources.

C.

the sources emit light of the same frequency.

D.

the sources emit light of the same amplitude. (1)

13

39.

A vibrating tuning fork is held above the top of a tube that is filled with water. The water gradually runs out of the tube until a maximum loudness of sound is heard. Which of the following best shows the standing wave pattern set up in the tube at this position? B.

A.

D.

C.

(1)

40.

Which of the following is a correct description of the Doppler effect? A.

Change in frequency of light due to motion of the source of light.

B.

Change in frequency of light due to relative motion between the source of light and the observer.

C.

Change in observed frequency of light due to relative motion between the source of light and the observer.

D.

Change in observed frequency of light due to change in velocity of the source of light. (1)

41.

In a double-slit experiment using coherent light of wavelength , the central bright fringe is observed on a screen at point O, as shown below. P coherent light O wavelength 

double slit

screen (not to scale)

At point P, the path difference between light arriving at P from the two slits is 4. Which of the following correctly describes the observed fringe pattern? nature of fringe at P

number of dark fringes between O and P

A.

bright

3

B.

bright

4

C.

dark

3

D.

dark

4 (1) 14

42.

A string with both ends fixed is made to vibrate in the second harmonic mode as shown by the dashed lines in the diagram below.

P Q

The solid line shows a photograph of the string at a particular instant of time. Two points on the string have been marked P and Q. Which of the following correctly compares both the period of vibration of P and Q and the average speed of P and Q? Period

Average speed

A.

same

same

B.

same

different

C.

different

same

D.

different

different (1)

43.

The diagram below represents the fundamental (first harmonic) standing wave of sound inside a pipe.

P

Q

pipe

Which of the following correctly represents the displacement of the air at P and Q? P

Q

A. B. C.

D.

(1) 15

44.

Which statement is true for standing (stationary) waves? A.

All points in the wave vibrate in phase.

B.

There is no energy in a standing wave.

C.

The wavelength of the wave is the distance between adjacent nodes.

D.

Neighbouring points in the wave have different amplitudes of vibration. (1)

45.

A stationary source of sound emits waves of wavelength λ, period T and speed V. The source now moves with speed v in a straight line away from a stationary observer. What are the wavelength and the speed of the wave as detected by the observer? wavelength

speed

A.

λ

V+v

B.

λ – vT

V

C.

λ

V–v

D.

λ + vT

V (1)

46.

Which two conditions are necessary for observable interference between two light beams? A.

meet at a point

constant phase difference

B.

constant phase difference

similar amplitude

C.

same frequency

similar amplitude

D.

similar amplitude

meet at a point (1)

47.

A standing wave is established on a string between two fixed points.

T A

B U C D

At the instant shown, point T is moving downwards. Which arrow gives the direction of movement of point U at this instant? A.

A

B.

B

C.

C

D.

D (1)

16

48.

The diagrams below show two standing wave patterns that are set up in a stretched string fixed at both ends. The frequency of pattern 1 is f1 and that of pattern 2 is f2.

The ratio

A.

pattern 1

frequency f1

pattern 2

frequency f2

f1 is f2

1 . 3

B.

2 . 3

C.

3.

D.

6. (1)

49.

Sound of a constant frequency f0 is being emitted by a sound source. An observer O travels in the direction shown at a speed of 0.1 v where v is the speed of sound.

observer O

sound source Which of the following gives the relationship between f0 and the frequency f of observed sound? A.

f = 1.1f0

B.

f0 < f < 1.1f0

C.

f = 0.9f0

D.

f0 > f > 0.9f0 (1

50.

The two graphs show the variation with time of the individual displacements of two waves as they pass through the same point.

The displacement of the resultant wave at the point at time T is equal to A.

x1 + x2.

B.

x1 – x2 .

C.

A1 + A2.

D.

A1 – A2. (1) 17

51.

A tube is filled with water and a vibrating tuning fork is held above its open end.

The tap at the base of the tube is opened. As the water runs out, the sound is loudest when the water level is a distance x below the top of the tube. A second loud sound is heard when the water level is a distance y below the top. Which of the following is a correct expression for the wavelength  of the sound produced by the tuning fork? A.

=y

B.

 = 2x

C.

=y−x

D.

 = 2(y − x) (1)

52.

A source S, moving at constant speed, emits a sound of constant frequency. The source passes by a stationary observer O, as shown below.

Which of the following shows the variation with time t of the frequency f observed at O as the source S approaches and passes by the observer?

(1)

18

MARK SCHEME! 1.

A [1]

2.

C [1]

3.

A [1]

4.

C

5.

A

[1] [1] 6.

D [1]

7.

A [1]

8.

B [1]

9.

A [1]

10.

C [1]

11.

B

12.

B

[1] [1] 13.

D [1]

14.

C [1]

15.

B

16.

A

[1] [1] 17.

A [1]

18.

C

19.

A [1]

20.

B [1]

21.

B [1]

22.

C [1]

23.

B [1]

24.

B

25.

D

[1] [1] 26.

B [1]

19

27.

B [1]

28.

C

29.

A

[1] [1] 30.

D [1]

31.

C [1]

32.

A [1]

33.

A [1]

34.

B [1]

35.

B

36.

A

[1] [1] 37.

A [1]

38.

B [1]

39.

C [1]

40.

C [1]

41.

B [1]

42.

B

43.

A

[1] [1] 44.

D [1]

45.

D [1]

46.

A

47.

D

[1] [1] 48.

A [1]

491.

B

50.

B

[1] [1] 51.

D

52.

C

[1] [1]

20