IGCSE · 3 · multiple choice
Waves · Question 3
Waves · Original GioPhysics question with a detailed, mark-by-mark answer guide.
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multiple choice1 mark
A ray of light travels from air into a transparent block of refractive index 1.5. The angle of incidence in air is 40°. What is the angle of refraction in the block? (sin 40° = 0.643)
- A
17°
- B
25°
- C
40°
- D
74°
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Answer overviewCorrect answer: B — 25°
01
1 markAnswer and reasoning
How to approach it
Predict from the governing principle before looking for a matching option. Then reject alternatives by checking direction, units, limiting behaviour or the physical meaning of each statement.
- 1
The correct choice is B: 25°
- 2
D applies the ratio the wrong way round. Light entering a denser medium bends towards the normal, so any answer larger than 40° can be rejected before a calculation is done.
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