A prism is made of glass of unknown refractive index. A parallel beam of light is incident on the face of the prism. The angle of minimum deviation is measured to be \(40^\circ.\) What is the refractive index of the material of the prism?
(The refracting angle of the prism is \(60^\circ.\))
1. \(1.43\)
2. \(1.33\)
3. \(1.50\)
4. \(1.53\)

At what angle should a ray of light be incident on the face of a prism of refracting angle \(60^{\circ}\) so that it just suffers total internal reflection at the other face? The refractive index of the material of the prism is \(1.524\).
1. \(29.75^\circ\)
2.\(19^\circ\)
3.\(17.23^\circ\)
4.\(19.57^\circ\)