A light beam in air enters a block of transparent material at an angle of 29.0?

Question

A light beam in air enters a block of transparent material at an angle of 29.0? with respect to the normal. After refraction it makes an angle of 19.0? with respect to the normal.

a) Find the index of refraction of the material.
(1.48) - RIGHT!

b) In a second setting, the light actually originates within the transparent material. It enters the surface at an angle of 37.2? with respect to the normal before emerging out in the air. What angle would it make with the surface of the material once it emerges out in the air?
Not Right! (52.8) Discuss this question

c) What is the critical angle for this situation (that was discussed in part b)?

d) What would be the new critical angle if we immerse the block in a liquid of 1.32 index of refraction?

Explanation / Answer

we assume refractive index for air as 1

1 x sin 29 = n x sin 19

n = 1.489

1.489 x sin 37.2 = 1 x sin t

sin t = 64.2 with the normal

so with the surface it makes = 25.8 degrees

critical angle = sin ^-1 1/1.489

= 42.19 degrees

critical angle = sin inverse n2/n1

n2 = medium which light enter after refraction

n1 = medium in which light originates

new critical angle = sin inverse 1.32 / 1.489

= 62.436 degrees

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