Light wave enters from medium 1 to medium 2. Its velocity in 2 me… - Vidyadip

MCQ

Light wave enters from medium $1$ to medium $2.$ Its velocity in $2$ medium is double from $1.$ For total internal reflection the angle of incidence must be greater than

✓
$30^{\circ}$
B
$60^{\circ}$
C
$45^{\circ}$
D
$90^{\circ}$

✓

Answer

Correct option: A.

$30^{\circ}$

$\frac{\mu_2}{\mu_1}=\frac{v_1}{v_2}=\frac{1}{2} \Rightarrow \frac{\mu_1}{\mu_2}=2\left(\mu_1>\mu_2\right)$
For total internal reflection
${ }_2 \mu_1=\frac{1}{\sin C} \Rightarrow \frac{\mu_1}{\mu_2}$
$=\frac{1}{\sin C} \Rightarrow 2=\frac{1}{\sin C} \Rightarrow C=30^{\circ}$
So, for total (Internal reflection angle of incidence must be greater than $30^{\circ}$.

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