Question

1. Three plane mirrors intersect at right angles. A beam of laser light strikes the first of them at an angle ? with respect to the normal

a)Show that when this ray is reflected off of the other two mirrors and crosses the original ray, the angle ? between these two rays will be ?=180?? 2?.

b)For what angle ? will the two rays be perpendicular when they cross?

2.A ray of light in diamond (index of refraction 2.42) is incident on an interface with water.

a)What is the largest angle the incident ray can make with the normal in diamond and not be totally reflected back into the diamond?

Answer 1

Answer 1

in a triangle sum of angles =90

angle of incidence =angle of reflection

from these 2 we get all the angles

sum of angles in a quadrilateral=360

so ?=360-(2?+2?+180-2?)

=> ?=180-2?

Answer 2

Refractive index of diamond n = 2.42

Let critical angle be C then sin C = 1/ n

                                              C = sin ^-1 ( 1/ 2.42 )

                                                  = 24.4 ^o

C is equal to  largest angle the incident ray canmake with the normal in diamond and not be totally reflected backinto the diamond = 24.4 ^o