Electronic Devices - Communications - Discussion

θc = sin-1(nr/ni).

Let's consider two different media - creatively named medium I (incident medium) and medium are (refractive medium).

nr is the refractive index of refractive medium (cladding), and ni is the refractive index of incident medium (core).

nr should be less than ni, for the light ray to bend away from the normal at the refractive medium.

Therefore, nr/ni is always less than unity.

What are n1 and n2?

The critical angles that angle which is boundary between reflection and refraction so the critical angle is that from which the reflection is to be started.

θ_c = sin-1(n2/n1).

θ_c = sin-1(1.73/1.82) = 71.90.

@Bhavin, no its angle of reflection which is 90 when a material is incident with critical angle. @Sundar is right.

Just easy critical angle is always is equal to 90 and in this question we can consider the approximate value.

Critical angle θ_c = sin^-1(n2/n1)

The critical angle is only defined when n2/n1 is less than 1.

n1 = 1.82
n2 = 1.73

θ_c = sin^-1(1.73/1.82)

θ_c = 71.90°

For more details:

http://en.wikipedia.org/wiki/Total_internal_reflection#Critical_angle

http://physicsnet.co.uk/a-level-physics-as-a2/waves/refraction/

I could not understand. Please help me.