The angle of a prism is \(A\). One of its refracting surfaces is silvered. Light rays falling at an angle of incidence \(2{A}\) on the first surface return back through the same path after suffering reflection at the silvered surface. The refractive index \(\mu,\) of the prism, is:
1. \(2\text{sin}A\)
2. \(2\text{cos}A\)
3. \(\dfrac{1}{2}\text{cos}A\)
4. \(\text{tan}A\)

A ray of light is incident at an angle of incidence, \(i\), on one face of a prism of angle \(A\) (assumed to be small) and emerges normally from the opposite face. If the refractive index of the prism is \(\mu,\) the angle of incidence \(i\), is nearly equal to:
1. \(\mu A\)
2. \(\frac{\mu A}{2}\)
3. \(\frac{A}{\mu}\)
4. \(\frac{A}{2\mu}\)

For the angle of minimum deviation of a prism to be equal to its refracting angle, the prism must be made of a material whose refractive index:

A thin prism of angle \(15^\circ\) made of glass of refractive index \(\mu_1=1.5\) is combined with another prism of the glass of refractive index \(\mu_1=1.75.\) The combination of the prism produced dispersion without deviation. The angle of the second prism should be:
1. \(5^\circ\)
2. \(7^\circ\)
3. \(10^\circ\)
4. \(12^\circ\)

A ray of light is incident on a \(60^\circ\) prism at the minimum deviation position. The angle of refraction at the first face (i.e. incident face) of the prism is:
1. \(30^\circ\)
2. \(45^\circ\)
3. \(60^\circ\)
4. zero