Question 1

What is the relation between focal length ($f$) and radius of curvature ($R$) of a spherical mirror?

Accepted Answer

The focal length of a spherical mirror is half of its radius of curvature, given by the formula $f = R/2$ under paraxial approximation.

Question 2

Which of the following phenomena is responsible for the working of optical fibres?

Accepted Answer

Optical fibres work on the principle of total internal reflection, where light signals travel inside the core without significant loss of energy.

Question 3

The critical angle for a pair of media depends upon:

Accepted Answer

The critical angle depends strictly on the refractive indices of the two media in contact, specifically the ratio of the refractive index of the rarer medium to that of the denser medium.

Question 4

When a light ray enters from a denser medium to a rarer medium:

Accepted Answer

When light travels from a denser to a rarer medium, it bends away from the normal because its speed increases in the rarer medium.

Question 5

The magnifying power of a simple microscope of focal length $f$ for a normal eye with least distance of distinct vision $D$ is:

Accepted Answer

When the final image is formed at the least distance of distinct vision, the magnifying power is given by $m = 1 + D/f$.

Ray Optics and Optical Instruments