Assertion `:` In optical fibre, the diameter of the core is kept small.
Reason `:` This smaller diameter of the core ensures that the fibre should have incident angle more than the critical angle required for total internal reflection.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion.
B. if both assertion and reason are true but reason is not the correct expalanation of the assertion
C. if assertion is true , but reason is false
D. both assertion and reason are false statements.

Answer

A

Explanation

Total internal reflection will be for rays incident at an angle greater than C. If the fibers. Are thin, only rays almost parallel will pass, further for non paraxial rays, the angle of incidecne is large and therefore, they also wil be totally internally reflected. Both are right.