A ray of light \(AO\) in vacuum is incident on a glass slab at angle \(60^\circ\) and refracted at angle \(30^\circ\) along \(OB\) as shown in the figure. The optical path length of light ray from \(A\) to \(B\) is:
1. | \( 2 a+2 b \) | 2. | \( \dfrac{2 \sqrt{3}}{a}+2 b \) |
3. | \( 2 a+\dfrac{2 b}{a} \) | 4. | \( 2 a+\dfrac{2 b}{\sqrt{3}}\) |
A transparent cube of side, made of a material of refractive index \(\mu_2\), is immersed in a liquid of refractive index \(\mu_1(\mu_1<\mu_2)\) . A ray is incident on the face \(AB\) at an angle \(\theta\) (shown in the figure). Total internal reflection takes place at point \(E\) on the face \(BC\).
Then \(\theta\) must satisfy:
1. \(\theta>\sin^{-1}\sqrt{\frac{\mu_2^2}{\mu_1^2}-1} \)
2. \(\theta<\sin^{-1}\sqrt{\frac{\mu_2^2}{\mu_1^2}-1} \)
3. \(\theta<\sin^{-1}\frac{\mu_1}{\mu_2}\)
4. \(\theta>\sin^{-1}\frac{\mu_1}{\mu_2}\)