Light enters at an angle of incidence in a transparent rod of refractive index \(n.\) For what value of the refractive index of the material of the rod, will the light, once entered into it, not leave it through its lateral face whatsoever be the value of the angle of incidence?

If refractive index of a prism is \(\mathrm{cot(A/2)}\), then the minimum angle of deviation is:
1. \(180^{\circ}-A\)
2. \(180^{\circ}-2A\)
3. \(90^{\circ}-A\)
4. \((A/2)\)

In a compound microscope, the magnification is \(95,\) the distance of the object from the objective lens is \(\left(\dfrac{1}{3.8}\right)~\text{cm}\) and the focal length of the objective is \(\dfrac{1}{4}~\text{cm}.\) What is the magnification of the eyepiece when the final image is formed at the least distance of distinct vision?
1. \(5\)
2. \(10\)
3. \(100\)
4. none of the above

A rainbow is formed due to:

A plane convex lens \((\mu= 1.5)\) has a radius of curvature \(10~\text{cm}\). It is silvered on its plane surface. The focal length of the lens after silvering is:

A tall man, of height \(6\) feet, wants to see his full image. The required minimum length of the mirror will be:

A disc is placed on the surface of a pond which has a refractive index of \(\frac{5}{3}.\) A source of light is placed \(4\) m below the surface of the liquid. Find The minimum radius of a disc so that light does not come out from it.
1. \(\infty\)
2. \(3~\text{m}\)
3. \(6~\text{m}\)
4. \(4~\text{m}\)

A ray of light travelling in the air has wavelength \(\lambda\), frequency \(n\), velocity \(v\), and intensity \(I\). If this ray enters into water then these parameters are \(\lambda', n', v'\) and \(I'\) respectively. Which relation is correct?
1. \(\lambda = \lambda'\)
2. \(n=n'\)
3. \(v=v'\)
4. \(I=I'\)

Optical fibre is based on:
1. Total internal reflection
2. Less scattering
3. Refraction
4. Less absorption coefficient