Light Waves
4 marks · NormalA student shines a ray of light at a glass block at an angle of 30° to the normal. The glass has a refractive index of 1.52.
State Snell's law (the law of refraction) in words.
Calculate the angle of refraction in the glass. Give your answer to 2 decimal places. ( refractive~index = \frac{sin~i}{sin~r} )
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media.
(b) 19.01° deg
Common mistakes: Not converting angles to degrees
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correct statement of Snell's law in words.
M1 (b) · 1 mark · Uses refractive index formula: n = sin i / sin r.
M2 (b) · 1 mark · Rearranges correctly for sin r.
A1 (b) · 1 mark · Evaluates r correctly to 2 decimal places (19.01°). Accept within rounding tolerance.
Worked solution
a) Snell's law: The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media.
b) Given: n = 1.52, i = 30° Rearrange for sin r: So: (to 2 decimal places)