UGC NET CSE | June 2016 | Part 2 | Question: 30

Question

Optical fiber uses reflection to guide light through a channel, in which angle of incidence is ____ the critical angle

• A. equal to
• B. less than
• C. greater than
• D. less than or equal to

Answer 1

ans is C angle of incidence must be greater than critical angle

if angle is equal or less then critical angle  it will bend along or  inside the surface respectively

Answer 2

Optical fiber works on the priciple of Total internal reflection

 Total internal reflection is a phenomenon which occurs when a propagating wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface.

Answer must be C

Please refer :https://en.wikipedia.org/wiki/Total_internal_reflection

Comments

Critical angle

The critical angle is the smallest angle of incidence that yields total reflection.[5] For light waves and other electromagnetic waves in isotropic media, there is a well-known formula for the critical angle in terms of the refractive indices.

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

Answer 3

 Ans is (3) greater than  
Angle of incidence must be greater than critical angle

The critical angle is the smallest angle of incidence that yields total reflection.

If angle is equal or less then critical angle  it will bend along or inside the surface respectively

Optical fiber works on the principle of Total internal reflection

Total internal reflection is a phenomenon which occurs when a propagating wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface.