AQA GCSE Physics Physics Paper 2 (Foundation), June 2025: Question 5

10 marks · Low Demand difficulty · Short Answer

Identify features of convex lenses, measure ray diagram dimensions to calculate magnification, and describe the transmission and absorption of light by colour filters.

Practise this question

Question

Question 5 shows diagrams and questions regarding convex lenses and light. Figure 6 shows parallel horizontal rays of light passing through a convex lens represented by a vertical line with arrows pointing outwards, converging at point X on the principal axis. Sub-questions ask to name point X, name the process of light bending, and select the shape of a convex lens. Figure 7 shows a ray diagram on a grid showing an upright virtual magnified image formed by a convex lens. Students are asked to measure the image height and object height, calculate magnification using the provided formula, explain why magnification has no units, and describe how white light interacts with colourless glass versus blue glass.

Mark scheme

Show the mark scheme Mark scheme for Question 5 with 10 total marks. 05.1: principal focus (1 mark). 05.2: refraction (1 mark). 05.3: first shape showing a biconvex lens ticked (1 mark). 05.4: image height = 2.0 cm and object height = 0.8 cm (1 mark). 05.5: magnification = 2.0 / 0.8 = 2.5, allowing ecf from 05.4 (2 marks). 05.6: magnification is a ratio (1 mark). 05.7: colourless glass transmits white/all colours of light (1 mark); blue glass transmits blue light (1 mark) and absorbs all other colours of light (1 mark).

How to answer it

Convex Lenses, Magnification & Colour Filters

💡 REVISION OVERVIEW

What This Question Tests

  • Optics Terminology: Identifying the principal focus, focal length, and the mechanism of refraction through converging lenses.
  • Lens Shapes: Distinguishing convex (converging) lenses from concave (diverging) lenses.
  • Ray Diagram Measurements & Magnification: Accurately reading object/image sizes from scaled diagrams and applying the magnification formula.
  • Absorption & Transmission of Light: Understanding how transparent colourless materials and coloured filters interact with white light.

Parts 05.1, 05.2 & 05.3: Lens Basics & Refraction

Foundational recall on convex lens anatomy and light behaviour

✅ Correct Answers

  • 05.1: Tick box 3: Principal focus [1 mark]
  • 05.2: Tick box 3: Refraction [1 mark]
  • 05.3: Tick box 1: The top shape (curved outward / thicker in the middle) [1 mark]

💡 Key Knowledge

  • Principal focus (F): The point where parallel rays of light converge after passing through a convex lens.
  • Focal length: The distance from the optical centre of the lens to the principal focus (not the point itself).
  • Refraction: Light waves change speed and bend when transitioning into a medium with a different optical density.
  • Convex lens: A converging lens that is thicker at the centre than at the edges.

❌ Common Errors

  • Confusing the point (principal focus) with the distance (focal length).
  • Mixing up refraction (wave bending through a boundary) with reflection (bouncing back).
  • Selecting the bottom diagram (concave/diverging lens, which curves inward).

Parts 05.4 & 05.5: Measuring & Calculating Magnification

Applying measurements from ray diagrams to determine scale factors

✅ Correct Answers

  • 05.4: Image height = 2.0 cm and Object height = 0.8 cm [1 mark for both]
  • 05.5: Magnification = 2.5 [2 marks]
Mark Breakdown (05.5):
• 1 mark for correct substitution: 2.0 / 0.8
• 1 mark for correct value: 2.5
Note: Error Carried Forward (ecf) is allowed if you mismeasured in 05.4.

📐 Calculation Walkthrough

  1. State equation:
    magnification = image height / object height
  2. Substitute values:
    magnification = 2.0 cm / 0.8 cm
  3. Calculate result:
    magnification = 2.5

🧠 Exam Technique

  • Always measure the arrow from the horizontal line (principal axis) straight up to the tip of the arrow head.
  • Even if your measurement in 05.4 is slightly off, you can still gain full marks in 05.5 via error carried forward by showing clear working.

Parts 05.6 & 05.7: Units & Colour Filters

Explaining dimensionless quantities and selective light transmission

✅ Correct Answers

  • 05.6: Tick box 3: Magnification is a ratio. [1 mark]
  • 05.7:
    Colourless glass: (White) light is transmitted. [1 mark]
    Blue glass: (Only) blue light is transmitted [1 mark], and all other colours (wavelengths/frequencies) are absorbed [1 mark].

💡 Key Knowledge

  • Why no units? Dividing a length (cm) by another length (cm) cancels out the units: cm / cm = 1 . It is a pure ratio.
  • Colourless transparent material: Transmits all wavelengths of visible light without absorbing any particular colour.
  • Colour filter: Absorbs specific wavelengths and only transmits the colour corresponding to the filter (e.g. blue filters absorb red, orange, yellow, green, violet).

❌ Common Errors

  • Saying blue glass "reflects" blue light. Glass filters are transparent; they work by transmission and absorption, not reflection.
  • Forgetting to mention what happens to the other colours in 05.7 (you must explicitly state that the other colours are absorbed to get all 3 marks).

Topics

Physics · P6: Waves

Question and mark scheme from the AQA GCSE Physics examination, Physics Paper 2 (Foundation), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.