AQA GCSE Physics Physics Paper 2 (Higher), November 2020: Question 3

13 marks · Standard Demand difficulty · Short Answer

Investigate the refraction of light at a boundary between air and glass, including experimental design, data analysis, uncertainty, and wave properties.

Practise this question

Question

A physics exam question about refraction containing five sub-questions (03.1 to 03.5) with a photo of a ray box (Figure 3), a line graph showing angle of refraction against angle of incidence (Figure 4), and various answer lines and tick boxes.
Question text

03 A student investigated the refraction of light at the boundary between air and glass.

Figure 3 shows the ray box used.

Figure 3

03.1 The ray of light from the ray box should be as narrow as possible.

Explain why using a wider ray would give less accurate results than using a

narrower ray.

[2 marks]

Figure 4 shows the results.

Figure 4

03.2 Estimate the angle of refraction when the angle of incidence is 80°.

Show on Figure 4 how you obtained your answer.

[2 marks]

Angle of refraction = °

03.3 Describe a method the student could have used to obtain the results shown in

Figure 4.

[6 marks]

03.4 The student repeated each measurement three times.

When the angle of incidence was 40° the three measured values for the angle of

refraction were

28° 25° 22°

Estimate the uncertainty in the angle of refraction when the angle of incidence

was 40°.

Show how you determine your estimate.

[2 marks]

12 ±

Uncertainty = °

03.5 What property of the light wave changes when it is refracted?

[1 mark]

Tick ( ) one box.

Colour

Frequency

Velocity

Mark scheme

Show the mark scheme The mark scheme for question 3 detailing answers and mark allocations for parts 03.1 through 03.5, including level descriptors for the 6-mark experimental design question.

Question 3

AO /

Question Answers Extra information Mark

Spec. Ref.

03.1 it is harder to judge where the 1 AO3

centre of a wider ray is 4.6.1.3

RPA9

causing a larger uncertainty (in allow increasing random errors 1

the measurements) (in the measurements)

03.2 line of best fit drawn and 1 AO3

extrapolated to 80 degrees 4.6.1.3

RPA9

41 (degrees) allow 40 to 43 (degrees) 1

Level 3: The design/plan would lead to the production of a valid AO1

03.3 5–6

outcome. All key steps are identified and logically sequenced. 4.6.1.3

RPA9

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

outcome. Most steps are identified, but the method is not fully 3–4

logically sequenced.

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

1–2

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

No relevant content 0

Indicative content:

• place a glass block on a piece of paper

• draw around the glass block

• use the ray box to shine a ray of light through the glass block

• mark the ray of light entering the glass block

• mark the ray of light emerging from the glass block

• join the points to show the path of the complete ray through the

block

• and draw a normal line at 90 degrees to the surface

• use a protractor to measure the angle of incidence

• use a protractor to measure the angle of refraction

• use a ray box to shine a ray of light at a range of different angles

(of incidence)

• increase the angle of incidence in 10 degree intervals

• from an angle of incidence of 10 degrees to an angle of

incidence of 70 degrees.

allow use of optical pins instead of a ray box

03.4 (28 + 25 + 22) 1 AO3

= 25

3 4.6.1.3 11

3 (degrees) 1

allow alternative method

28 – 22 = 6 (1)

= 3 (degrees) (1)

03.5 Velocity 1 AO1

4.6.2.2

Total 13

How to answer it

Investigating Refraction of Light (Required Practical)

What this question tests

This question assesses your knowledge and understanding of the Refraction Required Practical. You need to explain experimental design choices (like beam width), process and interpret graphical data (extrapolation), describe a multi-step practical procedure safely and accurately, calculate experimental uncertainty from repeat readings, and recall fundamental wave properties during refraction.

Question 03.1 (2 marks)

Explaining Ray Width and Uncertainty

✅ Correct Answer

  • It is harder to judge where the centre of a wider ray is (1 mark).
  • This causes a larger random error in the measurements (1 mark).

❌ Common Errors

Students often lose marks by simply stating "it makes the results inaccurate" without explaining why. You must link the width of the beam to the difficulty of locating the exact centre of the light ray when aligning a ruler or drawing pencil lines.

Question 03.2 (2 marks)

Extrapolating Graphical Data

✅ Correct Answer

  • Line of best fit drawn and extended (extrapolated) up to an angle of incidence of 80 degrees (1 mark).
  • Angle of refraction = 41° (Accept anywhere from 40° to 43°) (1 mark).

🧠 Exam Technique

When extending a trend line past your plotted points, use a sharp pencil and a clear plastic ruler so you can see the underlying grid lines. Always read values off the axes carefully to account for minor scale divisions.

Question 03.3 (6 marks)

Describing the Refraction Practical Procedure

💡 Key Knowledge (Required Practical Steps)

  • Place a glass block on a piece of paper and draw around it.
  • Use a ray box to shine a ray of light through the glass block.
  • Mark the ray entering and emerging from the glass block using crosses/pencil dots.
  • Remove the block and join the points to show the complete path of the ray.
  • Draw a normal line at 90 degrees to the surface where the ray enters.
  • Use a protractor to measure both the angle of incidence and the angle of refraction.
  • Repeat for a range of angles of incidence (e.g., from 10 degrees to 70 degrees at 10-degree intervals).

🧠 How Level 3 (5–6 marks) is Awarded

To secure top marks, your description must be logically sequenced so that another student could follow your instructions to get valid results. Mentioning equipment (ray box, protractor, paper) and specific measurements (angles in 10° intervals) distinguishes a top-tier response.

Question 03.4 (2 marks)

Calculating Experimental Uncertainty

📐 Step-by-Step Calculation

Method A (Mean-based):

  1. Calculate the mean: (28 + 25 + 22) / 3 = 25
  2. State uncertainty as half the range from the mean, or calculate max deviation: 28 - 25 = 3

Method B (Range-based / Alternative):

  1. Find the total spread: 28 - 22 = 6
  2. Divide the range by 2: 6 / 2 = 3
Uncertainty = ± 3 °

❌ Common Calculation Traps

Students often forget to divide the total range by 2 when calculating plus-minus (±) uncertainty. Remember: uncertainty is expressed as plus or minus half the range of repeated measurements.

Question 03.5 (1 mark)

Wave Properties During Refraction

✅ Correct Answer & Explanation

Tick the box for: Velocity

When light passes from air into a denser medium like glass, it slows down (its velocity decreases) and changes direction (refracts). Its frequency remains constant because frequency is determined by the source.

Topics

Physics · Required Practicals · P6: Waves · Required Practicals

Question and mark scheme from the AQA GCSE Physics examination, Physics Paper 2 (Higher), November 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.