Question

For 589 nm light, calculate the critical angle for the following materials surrounded by air.

(a) diamond
°
(b) flint glass
°
(c) sodium chloride
°

Part B.A glass fiber (n = 1.50) is submerged in water (n = 1.33). What is the critical angle for light to stay inside the optical fiber?

Answer 1

critical angle = sin^-1(1/n )

n =  index of refraction of the substances

sub part a )

diamond n = 2.419

critical angle = sin^-1(1/2.419) = 24.42 degee

sub part b )

for flint glass n = 1.66

critical angle = sin^-1(1/1.66) = 37.04 degee

sub part c )

for sodium chloride n = 1.54

critical angle = sin^-1(1/1.54) = 40.5 degee

PART b ) n1sinthetq1 = n2sintheta2

n1 = glass

n2 = water

critical angle is when theta = 90 ; sintheta2 = 1

theta = sin^-1(n2/n1)

theta = sin^-1(1.33/1.50) = 62.46 degree