Total Internal Reflection
3 marks · NormalA glass block has a refractive index of 1.48. Calculate: a) The value of sin of the critical angle. b) The value of the critical angle itself (to 2 decimal places).
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a) sin c = 1/1.48 = 0.676; b) c = arcsin(0.676) = 42.51°
Common mistakes: Incorrectly inverting n; Using tan instead of sin
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Marking points
M1 · 1 mark · Uses sin c = 1/n
A1 · 1 mark · Obtains sin c = 0.676 (accept rounding)
A2 · 1 mark · Obtains c = 42.51° (accept 42.5°–42.6° due to rounding)
Worked solution