AQA AS Physics

Topic Questions

3.1 Longitudinal & Transverse Waves

1a1 mark

State what is meant by a transverse wave.

1b3 marks

Give three examples of a transverse wave.

1c1 mark

State what is meant by a longitudinal wave.

1d2 marks

Give two examples of a longitudinal wave.

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2a2 marks

State what is meant by polarisation.

2b3 marks

Table 1

Type of Wave

Longitudinal or Transverse

Can be Polarised? (Yes / No)

Ultrasound

 

 

Microwaves

 

 

UV

 

 

 

Complete the missing information in the columns in Table 1 to show which of the waves listed are transverse or longitudinal and whether they can be polarised .

2c2 marks

Figure 1 shows unpolarised light directed towards a polarising filter A.

Figure 1

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Polarising filter B is placed directly after A and is identical except rotated by 90º. 

State and explain what happens to the light after it is incident on polarising filter B.

2d2 marks

Instead of unpolarised light, light polarised at an angle θ is incident on a vertically polarising filter A. 

Katie says that the light will become completely vertically polarised with no loss in intensity after polarising filter A. Jon says that the light will be vertically polarised with a reduced intensity after polarising filter A. 

State who is correct and clearly explain your answer.

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3a2 marks

State what is meant by the amplitude of a wave.

3b2 marks

Figure 1

3-1-s-q--q3b-easy-aqa-a-level-physics

Show on Figure 1: 

   (i)    The wave amplitude, A 

   (ii)    The time period, T of the vibrations of the wave

3c2 marks

Calculate the frequency of the wave in Figure 1.

3d3 marks

The wave in Figure 1 has a wavelength of 2 km. 

Calculate the speed of the wave.

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4a2 marks

State what is meant by a progressive wave.

4b1 mark

Figure 1 shows an example of a progressive wave.

Figure 1

3-1-s-q--q4b-easy-aqa-a-level-physics

Show on Figure 1 the wavelength λ of the wave.

4c1 mark

Explain what is meant by the phase difference between two points on a wave.

4d2 marks

Figure 2 shows some points on the progressive wave.

Figure 2

3-1-s-q--q4d-easy-aqa-a-level-physics

State which two points A, B, C or D are 

            (i)    in phase 

            (ii)    in anti–phase

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5a1 mark

Figure 1 shows a sound wave travelling to the right.

Figure 1

3-1-s-q--q5a-easy-aqa-a-level-physics

Show on Figure 1 the wavelength λ of the sound wave.

5b2 marks

Explain how energy is transmitted in this sound wave.

5c3 marks

The sound wave has a speed of 340 m s–1 and a wavelength of 11 m. 

Calculate the frequency of the sound wave.

5d3 marks

Hence or otherwise, calculate the time period of the sound wave.

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1a3 marks

Figure 1 shows a vertical cross-section through a water wave moving from left to right.

Figure 1

3-1-s-q--q1a-hard-aqa-a-level-physics

Deduce the point at which the water is moving at maximum speed and explain your reasoning. 

1b4 marks

While a microphone is connected to an oscilloscope, a student strikes a tuning fork nearby. 

The sound wave produced by the tuning fork is displayed as a trace on the screen. Figure 2 shows the resulting trace.

Figure 2

3-1-s-q--q1b-hard-aqa-a-level-physics

Use Figure 2 to calculate the wavelength of the sound wave produced. 

(The speed of sound is approximately 330 m s–1).

1c3 marks

The student’s lab partner strikes another identical tuning fork near the microphone, so that both sound wave signals can be overlaid on the oscilloscope trace. Figure 3 shows the new trace.

Figure 3

3-1-s-q--q1c-hard-aqa-a-level-physics

Using Figure 3, determine the phase difference between the two signals as shown on the oscilloscope trace. 

Give a suitable unit with your answer.

1d4 marks

The oscilloscope trace is known as a ‘time-view’ of the sound wave because it shows the displacement of an oscillating signal against time. One of the students makes a time-view sketch as shown in Figure 4a, including a label M. 

An oscillating signal can also be shown in terms of a ‘space-view’, which would show the displacement of the signal against its position. The other student makes a space-view sketch as shown in Figure 4b, including a label N.

Figure 4a

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Figure 4b

c7YeQlBD_3-1-s-q--q1d-image2-hard-aqa-a-level-physics

Show that the wave speed v is given by:

                  V=fraction numerator 3 N over denominator 2 M end fraction

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2a3 marks

Transverse progressive sinusoidal waves of wavelength λ travel along a horizontal rope. 

P and Q are points on the rope fraction numerator 5 lambda over denominator 4 end fraction apart and the waves travel from P to Q. 

With an appropriate sketch, discuss the motion of Q at the instant when P is displaced upwards but is moving downwards.

2b3 marks

Electromagnetic waves carry energy through the vacuum of space as progressive transverse waves. 

Discuss the motion of an electromagnetic wave with reference to the appropriate fields.

2c3 marks

Einstein famously discovered an equation called the ‘energy relation’, which gives the energy E of any particle in terms of its momentum p and mass m: 

                  E2 = (pc)2 + (mc2)2 

One of the surprising consequences from this equation is that electromagnetic waves also carry momentum p through the vacuum of space. 

Using knowledge of photons in the electromagnetic spectrum and Einstein’s energy relation, show that the photon momentum p is given by the equation: 

                  p =h over lambda

2d4 marks

Electromagnetic waves, being transverse, can also be polarised.

A light source is viewed through two pieces of polarisers, A and B, with their axes initially at straight pi over 2 radians from each other, as shown in Figure 1.

Figure 1

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Using the axes below, sketch the variation of intensity of light reaching the eye with angular displacement of B with respect to A when polariser B is rotated. 

3-1-s-q--q2d-image1-hard-aqa-a-level-physics

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3a3 marks

When electromagnetic waves are reflected from a shiny surface, such as a road sign, they often become polarised. 

Suggest how to determine experimentally if visible light reflected from a road sign is polarised.

3b2 marks

Changes in phase can also occur when electromagnetic waves are reflected from a surface. 

If an electromagnetic wave is reflected at the boundary between a medium with a higher refractive index than the medium it is travelling in, the oscillating electric field undergoes a phase change of π radians. 

Light is incident on an air-water boundary. A displacement-position sketch of the amplitude of the incident electric field is shown in Figure 1. The origin represents the boundary.

Figure 1

3-1-s-q--q3b-hard-aqa-a-level-physics

On Figure 1, sketch the amplitude of the reflected electric field.

3c3 marks

Three polaroid filters P1, P2 and P3 are aligned as shown in Figure 2. 

Unpolarised light is incident on P1 and subsequently passes through each of the three polaroid filters. P1 and P2 are fixed, but P3 can be rotated to any angle θ to that of P1.

Figure 2

3-1-s-q--q3c-hard-aqa-a-level-physics

Determine the angles of θ at which minima and maxima of emergent light intensity occur.

3d3 marks

In the spaces provided in Table 1, state whether the waves listed are polarised or unpolarised, and give a reason for your answer. 

Some of the spaces have been completed for you. 

Table 1

Wave

Polarised or Unpolarised

Reason

Light from the sun

 

 

Compression waves caused by an earthquake

Unpolarised

Longitudinal waves cannot be polarised

Electromagnetic waves emitted from a dipole aerial

 

 

Ultra-sonic waves from an echo sounder

 

 

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4a2 marks

Frequency and wavelength are fundamental properties of all waves. The relationship between them depends on the context of interaction and on the type of wave in question. 

Sketch a graph showing the relationship between the frequency and wavelength of an electromagnetic wave.

4b2 marks

Figure 1 shows the variation of air pressure with time of a sound wave.

Figure 1

dA2YuMD1_3-1-s-q--q4b-hard-aqa-a-level-physics

Sketch on Figure 1 separate graphs to show another sound wave of: 

   (i)         The same loudness but higher pitch. Label this graph X.

   (ii)        The same pitch but quieter. Label this graph Y.

4c3 marks

Figure 2a and Figure 2b shows the cross-sections of water waves produced by a plane wave vibration generator in a ripple tank. These waves are measured to move across the ripple tank at 20 cm s–1, travelling from left to right. 

A small fishing boat is shown on the water surface at O in Figure 2a. The same boat is then shown 0.2 seconds later at O’ in Figure 2b.

Figure 2a

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Figure 2b

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Calculate the wavelength of the water waves generated by the plane wave vibration generator.

4d2 marks

Discuss the motion of the boat during the next 0.2 s. 

State clearly any assumptions you make in your answer.

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1a4 marks

State what is meant by polarisation and explain how it is used to distinguish between transverse and longitudinal waves.

1b4 marks

An unpolarised light source passes horizontally through a fixed polarising filter A. An observer views the light emerging through a second polarising filter B, which may be rotated about point XY as shown in Figure 1.

Figure 1

3-1-s-q--q1b-medium-aqa-a-level-physics

The observer rotates B slowly through 360° clockwise. 

Relative to polarising filter A, at which angles of polarising filter B does the observer see the maxima and minima amount of daylight.

1c2 marks

On Figure 2 below, sketch how the light intensity reaching the observer varies as polarising filter B is rotated slowly through 360°.

Figure 2

3-1-s-q--q1c-medium-aqa-a-level-physics

1d2 marks

Explain why when the transmission axis of polarising filter B is perpendicular to the plane XY, the observer does not see horizontally polarised light. 

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2a2 marks

Figure 1 represents a progressive wave travelling from left to right on a stretched string.

Figure 1

3-1-s-q--q2a-medium-aqa-a-level-physics

The frequency of the wave is 30 Hz. Calculate the speed of the wave.

2b2 marks

State the phase difference between points X and Y on the string, giving an appropriate unit.

2c3 marks

Describe how the vertical displacement of point X on the string varies in the next period.

2d2 marks

Determine the phase difference between the current position of X and the position of X 0.0825 s later.

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3a3 marks

Explain briefly how transmission of energy by a longitudinal wave differs from transmission of energy by a transverse wave. Give one example of a transverse wave.

3b3 marks

With the aid of a clearly labelled diagram explain how a sound wave in air transmits energy away from its source.

3c3 marks

Short pulses of sound are reflected from a wall 30 m from the sound source. The reflected pulses return to the source after 0.18 s.

Calculate the speed of sound.

3d3 marks

Figure 1 represents the sound wave from part (c).

Figure 1

3-1-s-q--q3d-answer-medium-aqa-a-level-physics

Calculate the frequency of the sound wave.

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4a2 marks

Figure 1 shows two ways in which a wave can travel along a slinky spring.

Figure 1

3-1-s-q--q4a-medium-aqa-a-level-physics

Use arrows to draw the direction in which the points Q and R are about to move as each wave moves to the right.

4b3 marks

State which wave in part (a) electromagnetic waves are similar in nature to. 

Hence or otherwise, explain why it is important to correctly align a radio antenna in order to receive the strongest signal.             

4c2 marks

Light from a filament lamp is viewed through two polarising filters A and B shown in Figure 2.

Figure 2

3-1-s-q--q4c-medium-aqa-a-level-physics

Explain why the observer cannot see the light from the filament lamp.

4d3 marks

Explain how polaroid sunglasses can be used to view objects under the surface of water on a sunny day.

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5a2 marks

Explain the difference between compressions and rarefactions in a longitudinal wave.

5b3 marks

Musicians can use tuning forks to tune their instruments.

A tuning fork produces a specific frequency when it vibrates. 

Figure 1 shows a tuning fork vibrating in air at a single instant in time. The circles represent the positions of air particles in the sound wave.

Figure 1

3-1-s-q--q5b-medium-aqa-a-level-physics

The tuning fork is used to tune an orchestra at 0.44 kHz. 

Air particles vibrate in different phases in the direction in which the wave is travelling. 

Calculate the minimum separation of particles that vibrate 90° out of phase. 

            Speed of sound in air = 340 m s–1.     

5c2 marks

Figure 2 shows a snapshot of a progressive wave travelling from left to right on a violin string stretched between points X and Y. The violin is tuned to the same frequency as the tuning fork.

Figure 2

3-1-s-q--q5c-medium-aqa-a-level-physics

State the phase relationship between points A and B on the string. Label two more points, P and Q on Figure 2 which are  radians out of phase.

5d2 marks

Points X and Y in Figure 2 are 0.84 m apart. 

Calculate the speed of the wave travelling along the string.

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