Question

A laser beam strikes one end of a slab of material as shown in the figure below, in which ? = 50.0

Answer 1

apply snell's law

n1*sin(theta1)= n2*sin(theta2)

1*sin(50) = 1.48*sin(theta2)

sin(theta2) = sin(50)/1.48 = 0.517
theta2 = asin(0.517) = 31.13 degrees

hence the distamce travelled by the light FOR EAC REFLECTION IS 2d

here d is the base of the triangle
then

d = h/tan(31.13) = t/(2*tan(31.13)

t is the thickness of the rod which is not given in the problem.i think this may be given in the figure

2*d = t/tan(31.13)

the no.of internal reflections are N = length of slab/(2d)

N = 50/(2*d)

to calculate d we must know the thickness of the rod t which is not given in the problem.i think this may be given in the figure