question_answer 37)

  A short pulse of white light is incident from air to a glass slab at normal incidence. After travelling through the slab, the first colour to emerge is (a) blue                                (b) green (c) violet                              (d) red

Answer:

  (d) In air, all the colours of light travel with the same velocity, but in glass, velocities of different colours are different. Velocity of red colour is largest and velocity of violet colour is smallest. Therefore, after travelling through the glass slab, red colour will emerge first.