Question

Define absolute refractive index of an optical medium.

Hint:

Absolute refractive index = Speed in vacuum ÷ Speed in medium.

Answer 1

Definition of Absolute Refractive Index of an Optical Medium:

The absolute refractive index of an optical medium is defined as the ratio of the speed of light in vacuum to the speed of light in that medium.

Mathematical Expression:
n = c / v

Where:
n = absolute refractive index of the medium
c = speed of light in vacuum (approximately 3 × 10⁸ m/s)
v = speed of light in the given medium

Detailed Explanation:

1. When light travels from one medium to another, its speed changes.
2. The absolute refractive index measures how much the speed of light decreases in a medium compared to vacuum.
3. A higher value of refractive index means light travels slower in that medium.
4. For example, the refractive index of water is about 1.33, and for glass it is about 1.5.

Physical Meaning:
If the refractive index of a medium is 1.5, it means light travels 1.5 times faster in vacuum than in that medium.

Conclusion:
The absolute refractive index of an optical medium is the ratio of the speed of light in vacuum to its speed in that medium, and it indicates how much the medium slows down light.