NEET 2022, Physics Q38: Critical Angle and Total Internal Reflection

NEET2022Physics

Two transparent media A and B are separated by a plane boundary. The speed of light in those media are $1.5 \times 1 0^{8}$ m/s and $2.0 \times 1 0^{8}$ m/s, respectively. The critical angle for a ray of light for these two media is:

A
$sin^{- 1} (0.750)$
B
$tan^{- 1} (0.500)$
C
$tan^{- 1} (0.750)$
D
$sin^{- 1} (0.500)$

Solution

Total internal reflection is possible only when light travels from the denser medium (lower speed) to the rarer medium (higher speed). So A is denser.

Refractive index ratio: $\frac{μ _{r a r e}}{μ _{d e n se}} = \frac{v _{d e n se}}{v _{r a r e}} = \frac{1.5 \times 1 0 ^{8}}{2.0 \times 1 0 ^{8}} = 0.75$ .

Critical angle: $sin i_{c} = \frac{μ _{r a r e}}{μ _{d e n se}} = 0.75 \Rightarrow i_{c} = sin^{- 1} (0.750)$ .

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NEET 2022, Physics Q38: Critical Angle and Total Internal Reflection

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