AQA GCSE Combined Science: Trilogy Physics Paper 2 (Higher), 2023: Question 3

✅ Correct answer

• Measure across 8 wavelengths on Figure 4.
• Distance on Figure 4 is about 113 mm (mark scheme allows 108 mm to 118 mm).
• Convert using the scale: distance × 5.0
• Screen distance across 8 wavelengths = 113 × 5.0 = 565 mm
• One wavelength = 565 ÷ 8 = 70.6 mm
• Wavelength = 70 mm

📐 Calculation steps

1. Measure the total distance across 8 wavelengths on the figure.
2. Example measurement: 113 mm .
3. Convert to actual screen distance: 113 × 5.0 = 565 mm .
4. Find one wavelength: 565 ÷ 8 = 70.6 mm .
5. Round appropriately: 70 mm (or a value in the allowed range).

💡 Key knowledge

• Wavelength is the distance from one wave to the next matching point.
• On this image, it is more accurate to measure across several wavelengths and then divide.
• The scale says 1.0 mm on Figure 4 represents 5.0 mm on the screen, so you must multiply by 5.

🧠 Exam technique

• Show every stage of working, because this is how the method marks are awarded.
• Always measure across several waves, not just one gap.
• State the final answer with units: mm.
• Top answers clearly showed: total measured distance, scale conversion, then divide by 8.

❌ Common errors

• Forgetting to use the scale factor of 5.0.
• Measuring only one wavelength, which is less accurate.
• Dividing by the wrong number of wavelengths.
• Giving the measured figure distance instead of the actual screen wavelength.
• Missing off the unit mm.

✅ Correct answer

The mean is 97 mm for 5 measurements, so:

97 × 5 = 96 + 99 + 97 + X + 97

485 = 389 + X

X = 96

X = 96 mm

📐 Calculation steps

1. Use mean = total ÷ number of values.
2. Total of all 5 values = 97 × 5 = 485 .
3. Add the known values: 96 + 99 + 97 + 97 = 389 .
4. Find the missing value: 485 - 389 = 96 .

💡 Key knowledge

• Mean = total of values ÷ number of values.
• So total = mean × number of values.

🧠 Exam technique

• If a mean and one missing value are given, first find the total.
• Write the equation before solving it. This helps secure the method mark.
• Keep units consistent: here everything is in mm.

❌ Common calculation traps

• Adding the known values incorrectly.
• Dividing by 5 instead of multiplying by 5.
• Using only 4 values when finding the total from the mean.
• Forgetting that the mean includes the missing value too.

✅ Correct answer

Tick: The spread of values about the mean is very small.

💡 Key knowledge

• Precision means repeated values are close together.
• Accuracy means close to the true value.

🧠 Exam technique

• This is a common science vocabulary test: know the difference between precision and accuracy.
• If values are tightly grouped, that supports precision.

❌ Common errors

• Choosing “the mean value is very close to the true value” — that describes accuracy, not precision.
• Thinking “taken five times” automatically means precise. Repeats help, but precision is about how close the results are to each other.
• Thinking “nearest millimetre” proves precision. That only tells you the resolution used.

✅ Correct answer

• In longitudinal waves, the oscillations / vibrations are parallel to the direction of energy transfer.
• In transverse waves, the oscillations / vibrations are perpendicular to the direction of energy transfer.

💡 Key knowledge

• Parallel means in the same direction.
• Perpendicular means at 90° to the direction.
• Longitudinal examples include sound waves.
• Transverse examples include light waves and ripples on water at GCSE level.

🧠 Exam technique

• For 2 marks, make sure you compare both wave types.
• Use the key words parallel and perpendicular.
• Link your description to the direction of energy transfer to match the mark scheme exactly.

❌ Common errors

• Saying one wave moves “up and down” and the other “side to side” without linking to energy transfer.
• Mixing up parallel and perpendicular.
• Only describing one type of wave, which would lose a mark.

💡 What separated strong answers?

• Clear working in the wavelength and mean calculations.
• Accurate use of science vocabulary: precision, parallel, perpendicular.
• Correct units written in final answers.

❌ Where students lost marks

• Not converting the measured diagram distance using the scale.
• Confusing precision with accuracy.
• Giving vague wave definitions instead of using the accepted wording.

🧠 Best quick strategy

1. For measurements, measure across multiple waves.
2. For means, find the total first.
3. For multiple-choice science terms, check whether the question is about accuracy or precision.
4. For definitions, use exact comparison words from the specification.