A ray of light will go from diamond to glass. What should be the minimum angle of incidences at the surface of separation of the two media, diamond and glass, so that the ray of light cannot be refracted in glass ? `mu` of glass = 1.51 and `mu` of diamond = 2.47, `sin37.69^(@) = 0.61134`

Explanation

If the light ray is incident at the surface of separation of the media diamond and glass at critical angle, the grazingly refracted in glass. If the critical angle is `theta_(c)` then `sin theta_(c) = (1)/(g^(mu)d) = (1)/((mud)/(mug) ) = (mu_(g))/(mu_(d) )= (1.51)/(2.47)`
`= 0.61134 = sin37.69^(@)`
`therefore " " theta_(c) = 37.69^(@)`
So if the angle of incidence of a light ray is greater than `37.69^(@)` it cannot be refracted in glass.
`therefore` Required minimum angle of incidence = `37.69^(@)`.