AQA GCSE Combined Science: Trilogy Physics Paper 2 (Higher), 2019: Question 2

10 marks · Standard Demand difficulty · Extended Answer

Describe how to measure wavelength, frequency and wave speed in a ripple tank, explain why the duck’s motion shows water waves are transverse, and calculate the mean amplitude from repeated height measurements.

Practise this question

Question

The question page contains three linked parts about water waves in a ripple tank. Figure 3 is a labelled diagram of the apparatus: a shallow ripple tank of water on a stand, a wooden bar supported by elastic bands dipping into the water to create ripples, a support above the tank, a light source shining onto the water, and a screen below showing the ripple pattern; a horizontal double-headed arrow labelled distance is shown under the screen. Part 02.1 asks, for 6 marks, to describe how the equipment can be used to measure the wavelength, frequency and speed of a water wave. Figure 4 shows a plastic duck floating on a wavy water surface with a vertical double-headed arrow labelled movement of duck, and part 02.2 asks, for 1 mark, how this demonstrates that water waves are transverse. Part 02.3 gives a table of repeated measurements: maximum heights in mm are 509, 513 and 511; minimum heights in mm are 503, 498 and 499; it asks for a 3-mark calculation of the mean amplitude, with answer space labelled 'Mean amplitude = ___ mm'.
Question text

02 Figure 3 shows the equipment a teacher used to determine the speed of a

water wave.

The equipment includes:

• a ripple tank filled with water

• a wooden bar that creates ripples on the surface of the water

• a light source which causes a shadow of the ripples on the screen.

Figure 3

02.1 Describe how equipment in Figure 3 can be used to measure the wavelength,

frequency and speed of a water wave.

[6 marks]

The teacher put a plastic duck in the ripple tank as shown in Figure 4.

The plastic duck moved up and down as the waves in the water passed.

Figure 4

02.2 How does the movement of the plastic duck in Figure 4 demonstrate that water

waves are transverse?

[1 mark]

02.3 The teacher measured the maximum height and the minimum height of the plastic

duck above the screen as the wave passed.

The teacher repeated his measurements.

Table 2 shows the teacher’s measurements.

Table 2

*07* Maximum height in mm 509 513 511

Minimum height in mm 503 498 499

Calculate the mean amplitude of the water wave.

[3 marks]

Mean amplitude = mm

Mark scheme

Show the mark scheme The mark scheme shows question 02.1 as a level-of-response answer worth 6 marks, with Level 1 for some relevant steps, Level 2 for most steps identified but not fully sequenced, and Level 3 for a valid logically sequenced method. Indicative content includes measuring frequency with a stopclock by counting waves in a fixed time or using period and f = 1/T, measuring wavelength by freezing the image and measuring the distance across several wavefronts then dividing by the number of waves, and finding velocity either from v = fλ or by measuring distance travelled over time. For 02.2, the 1-mark answer is that the duck moves perpendicular to the direction of wave travel; 'duck moves up and down' alone is insufficient. For 02.3, the scheme gives mean maximum height 511 mm, mean minimum height 500 mm, difference 11 mm, then amplitude 11 divided by 2 equals 5.5 mm, with method marks for equivalent correct working.

AO /

Question Answers Mark ID

Spec. Ref.

02.1 Level 3: The design/plan would lead to the production of a valid 5–6 AO1 E

outcome. All key steps are identified and logically sequenced. 6.6.1.2

Level 2: The design/plan would not necessarily lead to a valid 3–4

outcome. Most steps are identified, but the plan is not fully

logically sequenced.

1–2

Level 1: The design/plan would not lead to a valid outcome.

Some relevant steps are identified, but links are not made clear.

No relevant content. 0

Indicative content

• If two quantities have been determined, v = f λ can be used to

find the third.

Frequency

• use a stopclock

• count the number of waves passing a point in a fixed time

period

• divide the time by the number of waves to determine the time

for one wave, T

• f = 1/T

• read the frequency off the oscillator

Wavelength

• use a camera to freeze the image

• use a metre rule to measure the distance between two

wavefronts

• count the number of waves between the wavefronts

• divide distance by the number of waves to determine λ

Velocity

• determine a mean value of frequency

• determine a mean value of wavelength

• measure the time it takes one wavefront to travel the length of

the screen

• measure the length of the screen

• speed = distance / time

to access Level 3 there must be a description of how frequency,

wavelength and velocity can be determined

02.2 (the duck) moves perpendicular duck moves up and down is 1 AO2 E

to the direction of wave travel insufficient 6.6.1.1

an answer of 5.5 gains 3 (mm)

02.3 marks AO2 E

mean maximum height = 511 1 6.6.1.2

and

mean minimum height = 500

511 – 500 = 11 allow a calculated difference 1

from incorrect means

11 / 2 = 5.5 (mm) allow their difference divided 1

by 2

any correct method of

determining the mean

amplitude can score 3 marks

Total 10

How to answer it

Ripple Tank Waves: wavelength, frequency, speed and amplitude

What this question tests
Plain revision summary: You need to describe how to measure wavelength, frequency, and speed using a ripple tank, explain why a duck moving up and down shows a transverse wave, and calculate amplitude from maximum and minimum heights. Marks are earned for using the correct method, linking it to the correct wave equation, and showing clear working with units.

Question overview

✅ Big idea

  • Use a ripple tank to observe water waves.
  • Measure wavelength from wavefront spacing.
  • Measure frequency by counting waves per time.
  • Use v = f × λ to find wave speed.

🧠 How marks are awarded

  • Method marks for describing the right steps.
  • Physics marks for correct wave ideas.
  • Calculation marks for correct means, difference, and halving.

Part (a) / 02.1 — Describe how to measure wavelength, frequency and speed

6 marks: full method needed for all three quantities

✅ Correct answer

  • Wavelength: use a metre rule to measure the distance between two wavefronts, or measure across several waves and divide by the number of wavelengths.
  • Frequency: use a stopwatch, count the number of waves passing a point in a fixed time, then calculate frequency using f = 1 / T or by dividing number of waves by time.
  • Speed: measure the wavelength and frequency, then use v = f × λ .

💡 Key knowledge

  • Wavelength, λ = distance between two matching points on adjacent waves, for example crest to crest or wavefront to wavefront.
  • Frequency, f = number of waves passing a point each second, in hertz (Hz).
  • Period, T = time for one wave, in seconds.
  • Wave speed, v = how fast the wave travels.

🧠 Exam technique

  • To reach top marks, describe the whole chain clearly: measure λ, measure f, then calculate v.
  • Make the steps logical and linked.
  • Use a camera or freeze-frame idea if explaining how to make the pattern easier to measure.
  • Always include units: m, s, Hz, m/s.

❌ Common errors

  • Saying only “measure the waves” is too vague.
  • Writing “speed = distance / time” without linking it to the wave measurements loses the key physics method.
  • Confusing frequency with wavelength.
  • Forgetting that wavelength is measured between identical points on successive waves.
  • Using “duck moves up and down” here would be irrelevant.

📐 Best full-mark structure

  1. Freeze or observe the ripple pattern clearly.
  2. Measure the distance across several wavefronts with a metre rule.
  3. Count how many waves are in that distance and divide to get λ .
  4. Use a stopwatch to count waves passing a point in a known time.
  5. Work out f from the number of waves per second, or use f = 1 / T .
  6. Calculate speed using v = f × λ .
Examiner insight: To access the top level, students had to explain all three measurements and show how they connect. Answers that only mentioned one quantity, or gave a formula with no method, were placed lower.

Part (b) / 02.2 — How does the duck show that water waves are transverse?

1 mark

✅ Correct answer

The duck moves perpendicular to the direction the wave travels.

💡 Key knowledge

In a transverse wave, the vibrations are at right angles to the direction of wave travel. The duck moving up and down shows the water particles vibrate vertically while the wave moves horizontally.

❌ Common errors

Saying only “the duck moves up and down” is not enough. You must link the movement to the direction of wave travel.

Examiner insight: The mark was awarded for the word perpendicular or an equivalent phrase like at right angles. Movement alone did not score.

Part (c) / 02.3 — Calculate the mean amplitude

3 marks

📐 Correct calculation

  1. Find the mean maximum height: (509 + 513 + 511) / 3 = 511 mm
  2. Find the mean minimum height: (503 + 498 + 499) / 3 = 500 mm
  3. Find the difference: 511 - 500 = 11 mm
  4. Amplitude is half the peak-to-trough height: 11 / 2 = 5.5 mm

✅ Final answer

Mean amplitude = 5.5 mm

🧠 Exam technique

  • Show the means clearly — you can still gain marks even if your method is slightly different.
  • Use the correct idea: amplitude is half the difference between maximum and minimum heights.
  • Keep the unit as mm.

❌ Common calculation traps

  • Adding the heights and dividing by the wrong number.
  • Forgetting to halve the difference.
  • Using one set of readings only instead of the mean values.
  • Writing the answer without units.

💡 Why this gets 3 marks

  • 1 mark for the mean maximum height, or an equivalent valid method.
  • 1 mark for the mean minimum height, or a correct difference method.
  • 1 mark for dividing by 2 to get amplitude.
Examiner insight: Students could still score full marks if they used a correct alternative method, as long as they found the mean amplitude correctly. The most common mistake was stopping at the peak-to-trough difference and not halving it.

Quick recall checklist

✅ Must-know facts

  • v = f × λ
  • f = 1 / T
  • Wavelength = distance between adjacent wavefronts.
  • Transverse = vibrations perpendicular to wave travel.
  • Amplitude = half the height from crest to trough.

🧠 What top answers do

  • Use precise scientific language.
  • Describe the method in a clear sequence.
  • Link measurements to equations.
  • Include units and sensible rounding.

Topics

Physics · P6: Waves

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Physics Paper 2 (Higher), 2019. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.