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Thin lens equation test with answers for AP Physics 2 (free PDF download)

Quick answer: Geometric optics treats light as rays. Reflection obeys θᵣ = θᵢ, refraction obeys Snell's law n₁ sin θ₁ = n₂ sin θ₂, and mirrors and thin lenses obey 1/dₒ + 1/dᵢ = 1/f with magnification m = −dᵢ/dₒ. This AP Physics 2 test on thin lens equation has 8 questions worth 20 marks, to do in 45 minutes: reflection, refraction into glass and total internal reflection. The mark scheme is on a separate page; free printable PDF.

Thin lens equation test with answers for AP Physics 2 (free PDF download)

This test covers the law of reflection, Snell’s law, total internal reflection and images from lenses and mirrors. It lasts 45 minutes and is worth 20 points. Use c = 3.00 × 10⁸ m/s and show every substitution with units.

Level: AP Physics 2 (algebra-based) · Curriculum: AP P2 Unit 13

Time: 45 minutes · 8 questions · Total: 20 marks · Calculator allowed

Question 1 Reflection (2 marks)

A ray strikes a plane mirror at 25° to the mirror surface.

  1. Calculate the angle of incidence. (1 mark)
  2. Calculate the angle between the incident and reflected rays. (1 mark)

Question 2 Refraction into glass (3 marks)

Light in air strikes glass of refractive index 1.60 at 50° to the normal. Use c = 3.00 × 10⁸ m/s.

  1. Calculate the speed of light in the glass. (1 mark)
  2. Calculate the angle of refraction. (2 marks)

Question 3 Total internal reflection (3 marks)

A glass has refractive index 1.55.

  1. Calculate the critical angle for glass in air. (2 marks)
  2. State the two conditions needed for total internal reflection. (1 mark)

Question 4 Image from a lens (4 marks)

A converging lens has f = 20 cm. An object 5.0 cm tall is 50 cm from the lens.

A converging lens with its focal points marked and an object arrow to the left of the lensFFobject
Lens and object (not to scale).
  1. Calculate the image distance. (2 marks)
  2. Calculate the magnification. (1 mark)
  3. Describe the image. (1 mark)

Question 5 Convex mirror (3 marks)

A convex mirror has f = −15 cm. An object is 45 cm from the mirror.

  1. Calculate the image distance. (2 marks)
  2. State whether the image is real or virtual, and upright or inverted. (1 mark)

Question 6 Diverging lens (2 marks)

Explain why a diverging lens cannot form a real image of a real object. (2 marks)

Question 7 Bent pencil (2 marks)

A pencil standing in a glass of water looks bent at the surface. Explain why. (2 marks)

Question 8 Sign convention (1 mark)

State the sign of the focal length of a converging lens and of a concave mirror. (1 mark)

See the thin lens equation test answers and mark scheme

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