Question

The speed of light in the medium is:
$
  {\text{A}}{\text{. minimum on the axis of the beam}} \\
  {\text{B}}{\text{. the same everywhere in the beam}} \\
  {\text{C}}{\text{. directly proportional to the intensity I}} \\
  {\text{D}}{\text{. maximum on the axis of the beam}} \\
 $

Answer 1

Hint: To answer this question we have to understand when light travels in vacuum it has maximum speed but when it travels in medium its speed decreases due to the refractive index of that medium. We have to understand the variation of the refractive index with the axis of the beam.

Complete step-by-step answer:

Now we have to understand the variation of speed of light with the axis of beam. That means with the variation of the refractive index.

The higher the refractive index the slower the light travels, which causes a correspondingly increased change in the direction of the light within the material. What this means for lenses is that a higher refractive index material can bend the light more and allow the profile of the lens to be lower.

Refractive Index of a medium depends upon the refractive index of the surroundings, optical density, wavelength of the light and temperature.
The speed of light in the medium is minimum on the axis of the beam, because the refractive index of the medium is maximum at the axis of the beam.

Hence option A is the correct option.

Note: Whenever we get this type of question the key concept of solving is we have to understand the variation of refractive index with the medium and with the axis of the medium. Then we would easily answer this type of question.