Question

Light travels in a line of optical fiber by total internal reflection between a core of refractive index 1.48 and a cladding 1.46 refractive index.

The critical angle for total internal reflection to occur inside the core of the fiber is ...

80.6º
48.8º
43.2º
42.5º
24.4º

I keep getting this one wrong too. Please help

Answer 1

For critical reflection, the angle of refraction in the less dense medium is 90 degrees.
Snell's Law says that, in this case,
1.46 sin 90 = 1.46 = 1.48 sin theta
theta = sin^-1 1.46/1.48 = sin^-1 0.9865
Look up the angle. It is one of your choices.

Answer 2

inverse sin--> =
Sin^-1(1.46-1.48)= 80.57 deg
90-80.57 = The Max_ang = 9.43 deg