14.2-Reflection of Light, Paper 2 (Section A)

Question 1

Light enters a parallel-sided glass block at A. The angle between the side of the block and the ray of light in the air is 35 degree.
The light then strikes the edge of the block at B. fig 7.7 shows the ray of the light and the glass block. (14.2) pg 1 (theory A)

The angle of refraction in the glass at A is 33 degree

a) Calculate the refractive index for light in the glass
b) The light undergoes total internal reflection at B
i) State one condition necessary for total internal reflection to occur
ii) On fig 7.7 continue the ray to show the path of the light after the total internal reflection at B and until it leaves the block

Answer 1

(a) (n=)sin i/sin r
=sin 55/sin 33
=1.5
(b)
i)angle of incidence greater than critical angle or denser to rarer medium
ii)reflected ray in correct direction (by eye) to edge of block and no second TIR (ign marked values)

Question 2

(a) On fig 3.1 mark the critical angle and label it c
(b) State why only one of the three rays is totally internally reflected
(c) Calculate:
i) the refractive index water
ii) the critical angle for the boundary between water and air

Answer 2

(a)middle ray angle of incidence labelled c
(b)angle of incidence (of right-handed ray only) greater than the critical angle
(c)
i)(n=)sin i/sin ralgebraic or numerical
=1.3
ii) sin c=1/n algebraic or numerical
answer in range 49 degree to 50.3 degree