GCSE Physics resources

AQA GCSE Waves

Light Required Practical

Use a ray box or narrow beam, mark the incident and refracted rays, draw the normal and measure angles. Keep the block shape and ray position controlled when comparing angles.

AQA 8463 GCSE Physics FoundationHigher

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The revision snapshot

Use a ray box or narrow beam, mark the incident and refracted rays, draw the normal and measure angles. Keep the block shape and ray position controlled when comparing angles.

By the end, you should be able to:

  • Investigate reflection and refraction.
  • Apply the waves model, evidence or method to an unfamiliar exam context.
  • Recognise and correct this wrong turn: Measuring from the block surface.

Before you revise

Diagnostic question

Choose an answer from memory. Your result tells you what to watch for in the guide.

Which statement correctly summarises light required practical?

Core revision guide

Learn the model, then use it

Light Required Practical questions become manageable when the central model, evidence and exam method are kept together. Read the explanation, test the misconception and then apply the idea without looking back.

Investigate reflection and refraction

Use a ray box or narrow beam, mark the incident and refracted rays, draw the normal and measure angles. Keep the block shape and ray position controlled when comparing angles.

Build the physics picture

Angles of incidence, reflection and refraction are measured from the normal, not the surface. Mark the ray positions with small crosses before removing the block so the line can be drawn accurately. A narrow ray and careful protractor reading reduce uncertainty.

A ray passes through a rectangular glass block with normals at both boundaries and emerges parallel with lateral displacement.
Measure angles from the normal, not from the surface; mark rays with crosses before removing the block.Open the full-size exam diagram

Misconception clinic

Replace the tempting answer

Read each belief, say what is wrong with it, then compare your correction.

Tempting idea: Measuring from the block surface.

Use instead: Use a ray box or narrow beam, mark the incident and refracted rays, draw the normal and measure angles. Keep the block shape and ray position controlled when comparing angles.

Tempting idea: Leaving the block in place when drawing internal rays without markers.

Use instead: Angles of incidence, reflection and refraction are measured from the normal, not the surface. Mark the ray positions with small crosses before removing the block so the line can be drawn accurately. A narrow ray and careful protractor reading reduce uncertainty.

Tempting idea: Using a broad unmarked beam.

Use instead: Show the normal, identify the measured angle, repeat readings and explain how ray thickness and protractor resolution affect uncertainty.

Retrieval practice

Quick checks

1. Which exam method is most reliable for light required practical?

2. Which statement correctly applies light required practical to a question?

3. A pupil writes: “Measuring from the block surface.” Which replacement is accurate?

Worked examples

See the method being built

These examples expose the difference between a secure investigate reflection and refraction method and the common error “Measuring from the block surface.”.

Example 1 · Reflection result

Incident angle is 42° to normal. Predict reflected angle.

  1. Use law of reflection.
  2. Angles from normal.
  3. State degrees.
Show the answer

Reflected angle = 42°.

Example 2 · Refraction method

Describe how to measure refraction through a glass block.

  1. Trace block, mark incident/refracted rays.
  2. Remove block and draw rays/normal.
  3. Measure from normal.
Show the answer

Use a narrow ray, mark positions, draw normal at boundary and measure angles with a protractor.

Example 3 · Uncertainty

A wide ray makes angle reading difficult. Improve.

  1. Identify broad ray as uncertainty.
  2. Narrow beam/slit.
  3. Use fine pencil marks.
Show the answer

Use a narrow ray box slit and thin pencil lines to reduce angular uncertainty.

Exam precision

Exam technique: Investigate reflection and refraction

Do this: Show the normal, identify the measured angle, repeat readings and explain how ray thickness and protractor resolution affect uncertainty.

Independent practice

Exam-style questions

Write an answer before opening the marking guidance. Then edit the exact phrase or step that would gain the next mark.

1. State what the normal is.

[1 mark]
Show marking guidance and model answer

Marking guidance: Award one mark for the precise statement shown in the model answer.

Model answer: A line perpendicular to the surface at the point where the ray meets it.

2. State the law of reflection.

[1 mark]
Show marking guidance and model answer

Marking guidance: Award one mark for the precise statement shown in the model answer.

Model answer: Angle of incidence equals angle of reflection.

3. Why measure angles from the normal?

[2 marks]
Show marking guidance and model answer

Marking guidance: 2 marks are available for relevant, linked physics points that match the model answer.

Model answer: The laws of reflection/refraction define angles relative to the normal.

4. Give one control variable in a glass-block refraction investigation.

[1 mark]
Show marking guidance and model answer

Marking guidance: Award one mark for the precise statement shown in the model answer.

Model answer: Use same block/material and same ray position/colour.

5. State why crosses are marked on ray paths.

[1 mark]
Show marking guidance and model answer

Marking guidance: Award one mark for the precise statement shown in the model answer.

Model answer: They allow accurate rays to be drawn after the block is removed.

6. Give one way to improve reliability.

[1 mark]
Show marking guidance and model answer

Marking guidance: Award one mark for the precise statement shown in the model answer.

Model answer: Repeat for each incident angle and compare/average readings.

Questions pupils ask

Light Required Practical FAQs

What is the main idea in Light Required Practical?

Use a ray box or narrow beam, mark the incident and refracted rays, draw the normal and measure angles. Keep the block shape and ray position controlled when comparing angles.

What mistake should I avoid in Light Required Practical?

Measuring from the block surface. Angles of incidence, reflection and refraction are measured from the normal, not the surface. Mark the ray positions with small crosses before removing the block so the line can be drawn accurately. A narrow ray and careful protractor reading reduce uncertainty.

Useful next steps

Connect this guide to your next task

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