A prism is made of glass of unknown refractive index. A parallel beam of light is incident on a face of the prism. The angle of minimum deviation is measured to be `40^@`. What is the refractive index of the material of the prism? The refracting angle of the prism is `60^@`. If the prism is placed in water (refractive index 1.33), predict the new angle of minimum deviation of a parallel beam of light.