NEET Physics Question - Ray Optics - Refraction by Plane Surfaces

Assertion (A): The refractive index of diamond is \(\sqrt{6}\), and that of liquid is \(\sqrt{3}\), . If the light travels from diamond to the liquid, it will totally reflected when the angle of incidence is \(30^\circ\).

Reason (R): For total internal reflection, angle of incidence should be less than critical angle \(\theta_c = sin^{-1}(\frac{1}{\mu})\).

Both (A) & (R) are true and the (R) is the correct explanation of the (A)

Both (A) & (R) are true but the (R) is not the correct explanation of the (A)

(A) is true but (R) is false

Both (A) and (R) are false

Solution:

The critical angle \(\theta_c = sin^{-1}(\mu_{liquid}/\mu_{diamond}) = sin^{-1}(\sqrt{3}/\sqrt{6}) = sin^{-1}(1/\sqrt{2}) = 45^\circ\), . For TIR, the angle of incidence (i), must be greater than \(\theta_c), (i.e., (i > 45^\circ),\). Since \(i = 30^\circ\), is not greater than \(45^\circ\), A is false. Reason R is also false because TIR occurs when \(i > \theta_c\).

Rankers Physics

Total Internal Reflection Conditions

Solution:

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