Question

The critical angle for a material X is 45°. The total internal reflection will take place, if the angle of incidence in the denser medium is:

Options

• less than 45°

• 90°

• more than 45°, but not 90°.

• less than 45°, but not zero degree

Answer 1

More than 45°, but not 90°.

Explanation:

Total internal reflection takes place when the angle of incidence in the denser medium is greater than the critical angle. Here, it must be greater than 45°. An angle less than the critical angle does not cause total internal reflection; the option with 90° is not the intended incidence condition for a ray crossing the surface.