Refraction

3 marks · Normal

A ray of light passes from air (speed in air = m/s) into glass (speed in glass = m/s). Calculate the refractive index of glass to two significant figures.

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1.5 (±0.02)

Also accept: 1.50

Common mistakes: Dividing the wrong way round

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Marking points

M1 · 1 mark · Uses the correct formula: n = speed in air / speed in glass

A1 · 1 mark · Correct substitution into the formula: n = 3.0e8 / 2.0e8

A1 · 1 mark · Final correct answer to 2 significant figures: 1.5 (accept 1.50) (follow-through)

Worked solution

So, the refractive index of glass is 1.5 (to two significant figures).