Waves revision [116 marks] - Peda.net...Waves revision [116 marks]1. A first-harmonic standing wave is formed on a vertical string of length 3.0 m using a vibration generator. The

Waves revision [116 marks]

1. A first-harmonic standing wave is formed on a vertical string of length 3.0 m using avibration generator. The boundary conditions for this string are that it is fixed at oneboundary and free at the other boundary.

The generator vibrates at a frequency of 300 Hz.

What is the speed of the wave on the string?

A. 0.90 km s

B. 1.2 km s

C. 1.8 km s

D. 3.6 km s

MarkschemeD

Examiners report[N/A]

–1

–1

–1

–1

Two travelling waves are moving through a medium. The diagram shows, for a point in

[1 mark]

2. Two travelling waves are moving through a medium. The diagram shows, for a point inthe medium, the variation with time t of the displacement d of each of the waves.

For the instant when t = 2.0 ms, what is the phase difference between the waves and what isthe resultant displacement of the waves?

MarkschemeD


3. The diagram shows an interference pattern produced by two sources that oscillate onthe surface of a liquid.

Which of the distances shown in the diagram corresponds to one fringe width of the interferencepattern?

MarkschemeC

[1 mark]

[1 mark]


4. A system that is subject to a restoring force oscillates about an equilibrium position.

For the motion to be simple harmonic, the restoring force must be proportional to

A. the amplitude of the oscillation.

B. the displacement from the equilibrium position.

C. the potential energy of the system.

D. the period of the oscillation.

MarkschemeB


5. A particle is displaced from rest and released at time t = 0. It performs simple harmonicmotion (SHM). Which graph shows the variation with time of the kinetic energy E of theparticle?

MarkschemeD

k

[1 mark]

[1 mark]


6. Two sound waves from a point source on the ground travel through the ground to adetector. The speed of one wave is 7.5 km s , the speed of the other wave is 5.0 km s. The waves arrive at the detector 15 s apart. What is the distance from the point source to the

detector?

A. 38 km

B. 45 km

C. 113 km

D. 225 km

MarkschemeD


–1 –

1

7. What is true about the acceleration of a particle that is oscillating with simple harmonicmotion (SHM)?

A. It is in the opposite direction to its velocity

B. It is decreasing when the potential energy is increasing

C. It is proportional to the frequency of the oscillation

D. It is at a minimum when the velocity is at a maximum

MarkschemeD


What are the changes in the speed and in the wavelength of monochromatic light when

[1 mark]

[1 mark]

8. What are the changes in the speed and in the wavelength of monochromatic light whenthe light passes from water to air?

MarkschemeA


9. A sound wave has a wavelength of 0.20 m. What is the phase difference between twopoints along the wave which are 0.85 m apart?

A. zero

B. 45°

C. 90°

D. 180°

MarkschemeC


10. A pair of slits in a double slit experiment are illuminated with monochromatic lightof wavelength 480 nm. The slits are separated by 1.0 mm. What is the separation ofthe fringes when observed at a distance of 2.0 m from the slits?

A. 2.4 × 10 mm

B. 9.6 × 10 mm

C. 2.4 × 10 mm

D. 9.6 × 10 mm

–4

–4

–1

–1

[1 mark]

[1 mark]

[1 mark]

MarkschemeD


11. A ray of light passes from the air into a long glass plate of refractive index n at an angleθ to the edge of the plate.

The ray is incident on the internal surface of the glass plate and the refracted ray travels alongthe external surface of the plate.

What change to n and what change to θ will cause the ray to travel entirely within the plate afterincidence?

MarkschemeA


A string stretched between two fixed points sounds its second harmonic at frequency f.

[1 mark]

12. A string stretched between two fixed points sounds its second harmonic at frequency f.

Which expression, where n is an integer, gives the frequencies of harmonics that have a nodeat the centre of the string?

A.

B. nf

C. 2nf

D. (2n + 1)f

MarkschemeB


fn+12

13a.

A beam of coherent monochromatic light from a distant galaxy is used in an optics experimenton Earth.

The beam is incident normally on a double slit. The distance between the slits is 0.300 mm. Ascreen is at a distance D from the slits. The diffraction angle θ is labelled.

A series of dark and bright fringes appears on the screen. Explain how a dark fringe isformed.

[1 mark]

[3 marks]

Markschemesuperposition of light from each slit / interference of light from both slits

with path/phase difference of any half-odd multiple of wavelength/any odd multiple of (inwords or symbols)

producing destructive interference

Ignore any reference to crests and troughs.

[3 marks]


π

13b. The wavelength of the beam as observed on Earth is 633.0 nm. The separationbetween a dark and a bright fringe on the screen is 4.50 mm. Calculate D.

Markschemeevidence of solving for D «D = »

« × 2» = 4.27 «m»

Award [1] max for 2.13 m.

[2 marks]


sdλ

4.50×10−3×0.300×10−3

633.0×10−9

The air between the slits and the screen is replaced with water. The refractive index of water is

[2 marks]

13c.

The air between the slits and the screen is replaced with water. The refractive index of water is1.33.

Calculate the wavelength of the light in water.

Markscheme = 476 «nm»

[1 mark]


633.01.33

13d. State two ways in which the intensity pattern on the screen changes.

Markschemedistance between peaks decreases

intensity decreases

[2 marks]


A loudspeaker emits sound towards the open end of a pipe. The other end is closed. A standing

[1 mark]

[2 marks]

14a.

A loudspeaker emits sound towards the open end of a pipe. The other end is closed. A standingwave is formed in the pipe. The diagram represents the displacement of molecules of air in thepipe at an instant of time.

Outline how the standing wave is formed.

Markschemethe incident wave «from the speaker» and the reflected wave «from the closed end»

superpose/combine/interfere

Allow superimpose/add up

Do not allow meet/interact

[1 mark]


14b.

X and Y represent the equilibrium positions of two air molecules in the pipe. The arrowrepresents the velocity of the molecule at Y.

Draw an arrow on the diagram to represent the direction of motion of the molecule at X.

MarkschemeHorizontal arrow from X to the right

MP2 is dependent on MP1

Ignore length of arrow

[1 mark]

[1 mark]

[1 mark]


14c. Label a position N that is a node of the standing wave.

MarkschemeP at a node

[1 mark]


14d. The speed of sound is 340 m s and the length of the pipe is 0.30 m. Calculate, in Hz,the frequency of the sound.

Markschemewavelength is λ = « =» 0.40 «m»

f = « » 850 «Hz»

Award [2] for a bald correct answer

Allow ECF from MP1

[2 marks]

–1

4×0.303

3400.40

[1 mark]

[2 marks]


14e.

The loudspeaker in (a) now emits sound towards an air–water boundary. A, B and C are parallelwavefronts emitted by the loudspeaker. The parts of wavefronts A and B in water are not shown.Wavefront C has not yet entered the water.

The speed of sound in air is 340 m s and in water it is 1500 m s .

The wavefronts make an angle θ with the surface of the water. Determine the maximum angle,θ , at which the sound can enter water. Give your answer to the correct number of significantfigures.

–1 –1

max

[2 marks]

Markscheme

θ = 13«°»


Award [2] for a bald answer of 13.1

Answer must be to 2/3 significant figures to award MP2

Allow 0.23 radians

[2 marks]


=sin θc

3401

1500

c

14f. Draw lines on the diagram to complete wavefronts A and B in water for θ < θ .

Markschemecorrect orientation

greater separation

Do not penalize the lengths of A and B in the water

Do not penalize a wavefront for C if it is consistent with A and B

MP1 must be awarded for MP2 to be awarded

[2 marks]


max

A series of dark and bright fringes appears on the screen. Explain how a dark fringe is

[2 marks]

15a. A series of dark and bright fringes appears on the screen. Explain how a dark fringe isformed.

Markschemesuperposition of light from each slit / interference of light from both slits

with path/phase difference of any half-odd multiple of wavelength/any odd multiple of (inwords or symbols)

producing destructive interference

Ignore any reference to crests and troughs.

[3 marks]


π

A beam of coherent monochromatic light from a distant galaxy is used in an optics experiment

[3 marks]

15b.

A beam of coherent monochromatic light from a distant galaxy is used in an optics experimenton Earth.

The beam is incident normally on a double slit. The distance between the slits is 0.300 mm. Ascreen is at a distance D from the slits. The diffraction angle θ is labelled.

Outline why the beam has to be coherent in order for the fringes to be visible.

Markschemelight waves (from slits) must have constant phase difference / no phase difference / be inphase

OWTTE

[1 mark]


The graph of variation of intensity with diffraction angle for this experiment is shown.

[1 mark]

15c.

The graph of variation of intensity with diffraction angle for this experiment is shown.

Calculate the angular separation between the central peak and the missing peak in thedouble-slit interference intensity pattern. State your answer to an appropriate numberof significant figures.

Markschemesin θ =

sin θ = 0.0084401…

final answer to three sig figs ( eg 0.00844 or 8.44 × 10 )

Allow ECF from (a)(iii).

Award [1] for 0.121 rad (can award MP3 in addition for proper sig fig)

Accept calculation in degrees leading to 0.481 degrees.

Award MP3 for any answer expressed to 3sf.

[3 marks]


4×633.0×10−9

0.300×10−3

–3

Deduce, in mm, the width of one slit.

[3 marks]

15d. Deduce, in mm, the width of one slit.

Markschemeuse of diffraction formula «b =

»

OR

«=» 7.5«00» × 10 «mm»

Allow ECF from (b)(i).

[2 marks]


λθ

633.0×10−9

0.00844

–2

15e. The wavelength of the light in the beam when emitted by the galaxy was 621.4 nm.

Explain, without further calculation, what can be deduced about the relative motion of the galaxyand the Earth.

[2 marks]

[2 marks]

Markschemewavelength increases (so frequency decreases) / light is redshifted

galaxy is moving away from Earth

Allow ECF for MP2 (ie wavelength decreases so moving towards).

[2 marks]


16a.

A small ball of mass m is moving in a horizontal circle on the inside surface of a frictionlesshemispherical bowl.

The normal reaction force N makes an angle θ to the horizontal.

State the direction of the resultant force on the ball.

Markschemetowards the centre «of the circle» / horizontally to the right

Do not accept towards the centre of the bowl

[1 mark]


On the diagram, construct an arrow of the correct length to represent the weight of the

[1 mark]

16b. On the diagram, construct an arrow of the correct length to represent the weight of theball.

Markschemedownward vertical arrow of any length

arrow of correct length

Judge the length of the vertical arrow by eye. The construction lines are not required. Alabel is not required

eg:

[2 marks]


Show that the magnitude of the net force F on the ball is given by the

[2 marks]

16c. Show that the magnitude of the net force F on the ball is given by thefollowing equation.

MarkschemeALTERNATIVE 1

F = N cos θmg = N sin θdividing/substituting to get result

ALTERNATIVE 2

right angle triangle drawn with F, N and W/mg labelled

angle correctly labelled and arrows on forces in correct directions

correct use of trigonometry leading to the required relationship

tan θ =

[3 marks]


F =mg

tan θ

=OA

mg

F

The radius of the bowl is 8.0 m and θ = 22°. Determine the speed of the ball.

[3 marks]

16d. The radius of the bowl is 8.0 m and θ = 22°. Determine the speed of the ball.

Markscheme = m

r = R cos θ

v =

v = 13.4/13 «ms »


Award [3] for an answer of 13.9/14 «ms ». MP2 omitted

[4 marks]


mg

tanθ

v2

r

√ /√ /√gRcos2θ

sin θ

gRcosθ

tanθ9.81×8.0cos22

tan22

–1

–1

Outline whether this ball can move on a horizontal circular path of radius equal to

[4 marks]

16e. Outline whether this ball can move on a horizontal circular path of radius equal tothe radius of the bowl.

Markschemethere is no force to balance the weight/N is horizontal

so no / it is not possible

Must see correct justification to award MP2

[2 marks]


The ball is now displaced through a small distance x from the bottom of the bowl and is then

[2 marks]

16f.

The ball is now displaced through a small distance x from the bottom of the bowl and is thenreleased from rest.

The magnitude of the force on the ball towards the equilibrium position is given by

where R is the radius of the bowl.

Outline why the ball will perform simple harmonic oscillations about the equilibriumposition.

Markschemethe «restoring» force/acceleration is proportional to displacement

Direction is not required

[1 mark]


mgx

R

16g. Show that the period of oscillation of the ball is about 6 s.

[1 mark]

[2 marks]

Markschemeω = «

» = «= 1.107 s »

T = « =

=» 5.7 «s»

Allow use of or g = 9.8 or 10

Award [0] for a substitution into T = 2π

[2 marks]


√ g

R√ 9.81

8.0–1

2πω2π

1.107

√ Ig

16h. The amplitude of oscillation is 0.12 m. On the axes, draw a graph to show the variationwith time t of the velocity v of the ball during one period.

[3 marks]

Markschemesine graph

correct amplitude «0.13 m s »

correct period and only 1 period shown

Accept ± sine for shape of the graph. Accept 5.7 s or 6.0 s for the correct period.

Amplitude should be correct to ± square for MP2

eg: v /m s

[3 marks]


–1

12

–1

17a. Outline how the standing wave is formed.

Markschemethe incident wave «from the speaker» and the reflected wave «from the closed end»

superpose/combine/interfere

Allow superimpose/add up

Do not allow meet/interact

[1 mark]


17b. Draw an arrow on the diagram to represent the direction of motion of the molecule at X.

[1 mark]

[1 mark]

MarkschemeHorizontal arrow from X to the right

MP2 is dependent on MP1

Ignore length of arrow

[1 mark]


17c. Label a position N that is a node of the standing wave.

MarkschemeP at a node

[1 mark]


17d. The speed of sound is 340 m s and the length of the pipe is 0.30 m. Calculate, in Hz,the frequency of the sound.

–1

[1 mark]

[2 marks]

Markschemewavelength is λ = « =» 0.40 «m»

f = « » 850 «Hz»


Allow ECF from MP1

[2 marks]


4×0.303

3400.40

17e. The speed of sound in air is 340 m s and in water it is 1500 m s .

The wavefronts make an angle θ with the surface of the water. Determine the maximum angle,θ , at which the sound can enter water. Give your answer to the correct number of significantfigures.

Markscheme

θ = 13«°»


Award [2] for a bald answer of 13.1

Answer must be to 2/3 significant figures to award MP2

Allow 0.23 radians

[2 marks]

–1 –1

max

=sin θc

3401

1500

c

[2 marks]


17f. Draw lines on the diagram to complete wavefronts A and B in water for θ < θ .

Markschemecorrect orientation

greater separation

Do not penalize the lengths of A and B in the water

Do not penalize a wavefront for C if it is consistent with A and B

MP1 must be awarded for MP2 to be awarded

[2 marks]


max

18. The graph shows the variation with time t of the velocity v of an objectundergoing simple harmonic motion (SHM). At which velocity does the displacementfrom the mean position take a maximum positive value?

MarkschemeD

[2 marks]

[1 mark]


19. What is the phase difference, in rad, between the centre of a compression and thecentre of a rarefaction for a longitudinal travelling wave?

A. 0

B.

C.

D.

MarkschemeC


π2

π

2π

20. Two wave pulses, each of amplitude A, approach each other. They then superposebefore continuing in their original directions. What is the total amplitude duringsuperposition and the amplitudes of the individual pulses after superposition?

MarkschemeD

[1 mark]

[1 mark]


21. The refractive index for light travelling from medium X to medium Y is . The refractive

index for light travelling from medium Y to medium Z is . What is the refractive index for lighttravelling from medium X to medium Z?

A.

B.

C.

D.

MarkschemeA


43

35

45

1512

54

2915

22. A pipe of fixed length is closed at one end. What is ?

A.

B.

C. 3

D. 5

MarkschemeC


third harmonic frequency of pipefirst harmonic frequency of pipe

15

13

The graph shows the variation with position s of the displacement x of a wave

[1 mark]

[1 mark]

23. The graph shows the variation with position s of the displacement x of a waveundergoing simple harmonic motion (SHM).

What is the magnitude of the velocity at the displacements X, Y and Z?

MarkschemeB


24. The diagram shows a second harmonic standing wave on a string fixed at both ends.

What is the phase difference, in rad, between the particle at X and the particle at Y?

A. 0

B.

C.

D.

MarkschemeA

π4π2

3π

4

[1 mark]

[1 mark]


25a.

A large cube is formed from ice. A light ray is incident from a vacuum at an angle of 46˚ to thenormal on one surface of the cube. The light ray is parallel to the plane of one of the sides of thecube. The angle of refraction inside the cube is 33˚.

Calculate the speed of light inside the ice cube.

Markscheme«v = c =»

2.3 x 10 «m s »


sin isin r

3×108×sin(33)sin(46)

8 –1

Show that no light emerges from side AB.

[2 marks]

25b. Show that no light emerges from side AB.

Markschemelight strikes AB at an angle of 57°

critical angle is «sin =» 50.1°

49.2° from unrounded value

angle of incidence is greater than critical angle so total internal reflection

OR

light strikes AB at an angle of 57°

calculation showing sin of “refracted angle” = 1.1

statement that since 1.1>1 the angle does not exist and the light does not emerge

[Max 3 marks]


–1( )2.33

25c. Sketch, on the diagram, the subsequent path of the light ray.

Markschemetotal internal reflection shown

ray emerges at opposite face to incidence

Judge angle of incidence=angle of reflection by eye or accept correctly labelled angles

With sensible refraction in correct direction


[3 marks]

[2 marks]

25d.

Each side of the ice cube is 0.75 m in length. The initial temperature of the ice cube is –20 °C.

Determine the energy required to melt all of the ice from –20 °C to water ata temperature of 0 °C.

Specific latent heat of fusion of ice = 330 kJ kgSpecific heat capacity of ice = 2.1 kJ kg kDensity of ice = 920 kg m

Markschememass = «volume x density» (0.75) x 920 «= 388 kg»

energy required to raise temperature = 388 x 2100 x 20 «= 1.63 x 10 J»

energy required to melt = 388 x 330 x 10 «= 1.28 x 10 J»

1.4 x 10 «J» OR 1.4 x 10 «kJ»

Accept any consistent units

Award [3 max] for answer which uses density as 1000 kg (1.5× 10 «J»)


–1

–1 –1

–3

3

7

3 8

8 5

–3 8

Outline the difference between the molecular structure of a solid and a liquid.

[4 marks]

25e. Outline the difference between the molecular structure of a solid and a liquid.

Markschemein solid state, nearest neighbour molecules cannot exchange places/have fixedpositions/are closer to each other/have regular pattern/have stronger forces of attraction

in liquid, bonds between molecules can be broken and re-form

OWTTE

Accept converse argument for liquids

[Max 1 Mark]


A particle undergoes simple harmonic motion (SHM). The graph shows the variation of

[1 mark]

26. A particle undergoes simple harmonic motion (SHM). The graph shows the variation ofvelocity v of the particle with time t.

What is the variation with time of the acceleration a of the particle?

MarkschemeA


27. What statement about X-rays and ultraviolet radiation is correct?

A. X-rays travel faster in a vacuum than ultraviolet waves.

B. X-rays have a higher frequency than ultraviolet waves.

C. X-rays cannot be diffracted unlike ultraviolet waves.

D. Microwaves lie between X-rays and ultraviolet in the electromagnetic spectrum.

MarkschemeB

[1 mark]

[1 mark]


28. Two pulses are travelling towards each other.

What is a possible pulse shape when the pulses overlap?

MarkschemeA


Unpolarized light of intensity I is incident on the first of two polarizing sheets. Initially

[1 mark]

29. Unpolarized light of intensity I is incident on the first of two polarizing sheets. Initiallythe planes of polarization of the sheets are perpendicular.

Which sheet must be rotated and by what angle so that light of intensity can emerge fromthe second sheet?

MarkschemeC


0

I0

4

30. When a sound wave travels from a region of hot air to a region of cold air, it refracts asshown.

What changes occur in the frequency and wavelength of the sound as it passes from the hot airto the cold air?

[1 mark]

[1 mark]

MarkschemeB


31. In simple harmonic oscillations which two quantities always have opposite directions?

A. Kinetic energy and potential energy

B. Velocity and acceleration

C. Velocity and displacement

D. Acceleration and displacement

MarkschemeD


32. A girl in a stationary boat observes that 10 wave crests pass the boat every minute.What is the period of the water waves?

A. min

B. min

C. 10 min

D. 10 min

MarkschemeA


110

110

–1

–1

The graph shows the variation with distance x of the displacement of the particles of a

[1 mark]

[1 mark]

33. The graph shows the variation with distance x of the displacement of the particles of amedium in which a longitudinal wave is travelling from left to right. Displacements to theright of equilibrium positions are positive.

Which point is at the centre of a compression?

A. x = 0

B. x = 1 m

C. x = 2 m

D. x = 3 m

MarkschemeB


34. A beam of unpolarized light is incident on the first of two parallel polarizers. Thetransmission axes of the two polarizers are initially parallel.

The first polarizer is now rotated about the direction of the incident beam by an anglesmaller than 90°. Which gives the changes, if any, in the intensity and polarization of thetransmitted light?

[1 mark]

[1 mark]

MarkschemeA


35. The frequency of the first harmonic standing wave in a pipe that is open at both ends is200 Hz. What is the frequency of the first harmonic in a pipe of the same length that isopen at one end and closed at the other?

A. 50 Hz

B. 75 Hz

C. 100 Hz

D. 400 Hz

MarkschemeC


36. A travelling wave of period 5.0 ms travels along a stretched string at a speed of 40 m s. Two points on the string are 0.050 m apart.

What is the phase difference between the two points?

A. 0

B.

C.

D. 2

MarkschemeB


–

1

π2

π

π

[1 mark]

[1 mark]

37. Properties of waves are

I. polarizationII. diffractionIII. refraction

Which of these properties apply to sound waves?

A. I and IIB. I and IIIC. II and IIID. I, II and III

MarkschemeC


38. Water is draining from a vertical tube that was initially full. A vibrating tuning fork is heldnear the top of the tube. For two positions of the water surface only, the sound is at itsmaximum loudness.

The distance between the two positions of maximum loudness is x.

What is the wavelength of the sound emitted by the tuning fork?

A.

B. x

C.

D. 2x

MarkschemeD

x2

3x

2

[1 mark]

[1 mark]


39a. Outline what is meant by the principle of superposition of waves.

Markschemewhen 2 waves meet the resultant displacement

is the «vector» sum of their individual displacements

Displacement should be mentioned at least once in MP 1 or 2.


Red laser light is incident on a double slit with a slit separation of 0.35 mm.

[2 marks]

39b. Red laser light is incident on a double slit with a slit separation of 0.35 mm.A double-slit interference pattern is observed on a screen 2.4 m from the slits.The distance between successive maxima on the screen is 4.7 mm.

Calculate the wavelength of the light. Give your answer to an appropriate number of significantfigures.

Markschemeλ =

= 6.9 x 10 «m»

answer to 2 SF

Allow missed powers of 10 for MP1.


4.7×10−3×0.35×10−3

2.4

–7

Explain the change to the appearance of the interference pattern when the red-light

[3 marks]

39c. Explain the change to the appearance of the interference pattern when the red-lightlaser is replaced by one that emits green light.

Markschemegreen wavelength smaller than red

fringe separation / distance between maxima decreases

Allow ECF from MP1.


39d. One of the slits is now covered.

Describe the appearance of the pattern on the screen.

[2 marks]

[2 marks]

Markschemebright central maximum

subsidiary maxima «on either side»

the width of the central fringe is twice / larger than the width of the subsidiary/secondaryfringes/maxima

OR

intensity of pattern is decreased

Allow marks from a suitably labelled intensity graph for single slit diffraction.


A student investigates how light can be used to measure the speed of a toy train.

40a.

A student investigates how light can be used to measure the speed of a toy train.

Light from a laser is incident on a double slit. The light from the slits is detected by a lightsensor attached to the train.

The graph shows the variation with time of the output voltage from the light sensor as the trainmoves parallel to the slits. The output voltage is proportional to the intensity of light incident onthe sensor.

Explain, with reference to the light passing through the slits, why a series of voltagepeaks occurs.

[3 marks]

Markscheme«light» superposes/interferes

pattern consists of «intensity» maxima and minimaORconsisting of constructive and destructive «interference»

voltage peaks correspond to interference maxima


40b. The slits are separated by 1.5 mm and the laser light has a wavelength of 6.3 x 10 m.The slits are 5.0 m from the train track. Calculate the separation between two adjacentpositions of the train when the output voltage is at a maximum.

Markscheme« » 2.1 x 10 «m»

If no unit assume m.Correct answer only.


–7

s = = =λDd

6.3×10−7×5.01.5×10−3

–3

Estimate the speed of the train.

[1 mark]

40c. Estimate the speed of the train.

Markschemecorrect read-off from graph of 25 m s

v = « » 8.4 x 10 «m s »

Allow ECF from (b)(i)


= =xt

2.1×10−3

25×10−3–2 –1

40d. In another experiment the student replaces the light sensor with a sound sensor. Thetrain travels away from a loudspeaker that is emitting sound waves ofconstant amplitude and frequency towards a reflecting barrier.

The sound sensor gives a graph of the variation of output voltage with time along the track thatis similar in shape to the graph shown in the resource. Explain how this effect arises.

[2 marks]

[2 marks]

Printed for Jyvaskylan Lyseon lukio

© International Baccalaureate Organization 2019 International Baccalaureate® - Baccalauréat International® - Bachillerato Internacional®

MarkschemeALTERNATIVE 1

«reflection at barrier» leads to two waves travelling in opposite directions

mention of formation of standing wave

maximum corresponds to antinode/maximum displacement «of air molecules»ORcomplete cancellation at node position


Documents

Waves revision [116 marks] - Peda.net...Waves revision [116 marks]1. A first-harmonic standing wave is formed on a vertical string of length 3.0 m using a vibration generator. The