Question

Speed of light is maximum in:
A. Glass
B. Vacuum
C. Water
D. Nylon

Answer 1

Hint: Speed of light is dependent on the refractive index of the medium. To understand this concept, you remind Huygens’s theory of light. Refractive index is nothing but opposition to the flow of light. Solid has higher refractive index since molecule in the solid are more close.

Complete step-by-step answer:
Light is an electromagnetic radiation that consists of transverse electromagnetic waves which travel with a speed of $3 \times 10^8$ m/s in vacuum. For visible light wavelength range from 3600 ${{A}^{0}}$to 7500${{A}^{0}}$ ($1{{A}^{0}}={{10}^{-10}}m$). If medium changes then velocity and wavelength changes but frequency remains unchanged. It is given that the medium velocity of a light remains constant.
A wave of light of single frequency is called monochromatic light. Example LASER. Sodium vapour lamp image yellow light which is considered as monochromatic light for practical purposes. The color of light is determined by frequency wavelength. A monochromatic light when traveling in the same area follows a straight line path.
Refractive index of any denser medium is greater than 1. The velocity of light in a rarer medium is greater than its velocity in any denser medium. This conclusion is in total agreement with the experimental results.
We all know that vacuum has no density. While glass and water and nylon is denser.
So the speed of light is maximum in vacuum.
Answer- (B)

Note: Speed of light is always maximum in vacuum and then air. Since the refractive index of air is one. Speed and velocity has a very fine line between them. Velocity is nothing but displacement per unit time and speed is the distance per unit time. Means we can say that from distance and time we can define speed.