Question

When a flat slab of transparent material is placed under water, the critical angle for light traveling from the slab into water is found to be 60°. What will the critical angle be if the slab is surrounded by air? Take the index of refraction for water to be 1.33. d) 45.6 c) 44.2 e) 47.3 a) 40.6 b) 42.5

Answer 1

(a) 40.6 degree

Step-by-step explanation:

When refraction takes place from slab to water, the critical angle is 60 degree.

Use Snell's law

refractive index of water with respect to slab

`\mu _(w)^(s)=(Sin60)/(Sin90)`

`(\mu _(w))/(\mu _(s))=0.866`

`(1.33)/(\mu _(s))=0.866`

μs = 1.536

Now for slab air interface, the critical angle is C.

`\mu _(a)^(s)=(SinC)/(Sin90)`

`(\mu _(a))/(\mu _(s))=(SinC)/(Sin90)`

1 / 1.536 = Sin C

C = 40.6 degree