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GCSE questions on refraction and TIR

Q8. The diagram shows a ray of light travelling through a semicircular glass block. The angle of incidence is labelled 'i'

(a)

(i) The angle of incidence i equals the critical angle for the glass.

Complete the diagram to show what happens to the ray of light at the glass-to-air boundary.

See the diagram

[1 mark]

(ii) The critical angle for the glass is 41°. Calculate the refractive index of the glass.

n = 1/sin c

1/sin 41o = 1.5

[2 marks]

(b) The diagram below shows what happens to a ray of light as it meets the boundary between air and water.

The refractive index of the water is 1.3

Calculate the angle of refraction r.

refractive index = sine of the angle of incidence/sine of the angle of refraction

n = (sin of i)/(sin of r)

1.3 = sin 35o/ (sin r)

sin r = 0.57/1.3

sin r = 0.44

r = 26o

 

[3 marks]

(Total 6 marks)