Question

When light is going from vacuum to another medium, then the value of refractive index is called:

• A. Relative refractive index
• B. Absolute refractive index
• C. Critical angle
• D. None

Answer 1

Answer: (B)

Absolute refractive index

Absolute refractive Index of a medium w.r.t. vacuum is defined as the ratio of speed of light $\left(c\right)$ in vacuum to the speed of light $\left(v\right)$ in the medium.

$\mu =\frac{c}{v}=\frac{Speedoflightinvacuum}{Speedoflightinmedium}$

Relative refractive Index of a medium 2 w.r.t. medium 1 is defined as the ratio of speed of light $\left(v_1\right)$ in medium 1 to the speed of light $\left(v_2\right)$ in medium 2.

$\mu =\frac{v_1}{v_2}=\frac{Speedoflightinmedium1}{Speedoflightinmedium2}$

Hence, the correct answer is OPTION B.