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10.Wave Optics
hard
Figure shown plane waves refracted for air to water using Huygen's principle $a, b, c, d, e$ are lengths on the diagram. The refractive index of water wrt air is the ratio.
A
$a/e$
B
$b/e$
C
$b/d$
D
$d/b$
Solution
By Huygen's Principle:
Time for the path length $(b)$ in air $=$ Time for path length $(d)$ in water.
$\Rightarrow \frac{b}{C_{a}}=\frac{d}{C_{w}},$ where $C_{a}$ is the speed of light in air, $C_{w}$ is the speed of light in water.
$\Rightarrow \frac{C_{a}}{C_{w}}=\frac{b}{d}$
from the definition of refractive index, $\mu_{w}=\frac{C_{a}}{C_{w}}=\frac{b}{d}$
Standard 12
Physics
