AQA GCSE Physics Physics Paper 2 (Foundation), June 2022: Question 9

✅ Model Answer Structure (6 Marks)

• Place a glass block on a piece of plain paper and draw around its outline with a pencil.
• Use a ray box (with a single slit) to shine a ray of light into one side of the glass block.
• Mark the path of the incoming (incident) ray and the emerging ray using cross-marks or dots.
• Remove the glass block and use a ruler to join the points, completing the ray path through the block.
• Draw a normal line (at 90 degrees) to the surface of the block at the point where the ray enters, using a protractor.
• Use a protractor to measure the angle of incidence and the angle of refraction. Repeat for a range of angles (e.g., 10° to 80° in 10° intervals).

🧠 Exam Technique (Levels of Response)

This is a 6-mark Level of Response question. To hit Level 3 (5–6 marks), your answer must be logically sequenced so that someone else could pick up your instructions and successfully replicate the experiment to gather valid data.

❌ Common Errors

• Describing an investigation involving mirrors and reflection instead of refraction (scores 0 marks).
• Forgetting to draw around the block before marking ray entry/exit points.
• Failing to mention the use of a protractor or normal line.

✅ Correct Answers & Mark Breakdown

• Axis Labelling (1 mark): Angle of incidence in degrees / ° on the x-axis, and angle of refraction in degrees / ° on the y-axis (must include units).
• Plotting Data (2 marks): All remaining points plotted correctly. (Allow 1 mark if 3 or 4 points are plotted correctly within half a small square tolerance).
• Line of Best Fit (1 mark): A smooth, curved line of best fit drawn through the points.

💡 Key Knowledge

The relationship between the angle of incidence and angle of refraction for glass is non-linear, which is why a curved line of best fit is required rather than a straight line with a ruler.

❌ Common Calculation & Graph Traps

Never force a curve through the origin if the trend of the data or physics principle does not dictate it, unless specified. Always use a sharp pencil for plotting crosses (not dots or blobs) and a smooth freehand motion for curves.

✅ Correct Answers (2 Marks)

• Mark 1: Normal line drawn as a dashed or solid line at 90° to the mirror surface precisely where the incident ray strikes it.
• Mark 2: Straight reflected ray drawn using a ruler, ensuring the angle of reflection equals the angle of incidence.

🧠 Exam Technique

Always use a sharp pencil and a ruler for optical ray diagrams. Even if the mark scheme says "ignore arrows", it is best practice to include arrows pointing away from the mirror on the reflected ray to clearly show the direction of light travel.

✅ Correct Answers (Any Two, 4 Marks Total)

• The protractor is drawn directly on the paper in Method A, meaning you do not have to move the mirror/protractor to measure angles (1 mark) , making it more likely to record the correct angle without introducing alignment errors (1 mark) .
• The ray in Method A uses a laser, which does not diverge as much as a ray box with a single slit (1 mark) , making it thinner and easier to judge the precise center/position of the ray (1 mark) .

💡 Key Knowledge

When comparing experimental setups in GCSE Physics, look out for systematic errors (like having to move measuring equipment between readings, which alters alignment) and precision (such as beam width/divergence).

❌ Common Errors

Vague answers like "Method A is more accurate" without explaining why (e.g., because the laser beam is thinner or the protractor is fixed) will fail to gain credit. Examiners require specific technical reasoning.