Question

1. By drawing a neat diagram, trace the path of ray of white light, through an equiangular glass prism, till it emerges out of a prism and strikes a white screen.
2. Write the sequence of colours formed on the white screen from bottom upward.
3. What is your observation, if white screen is replaced by a green screen? Give a reason.

Answer 1

(a)

White light enters the prism and splits into its seven colours. This splitting is called dispersion. Each colour bends towards the base of the prism by a different amount. Red is deviated the least and violet the most, so the colours come out spread apart and form a spectrum on the white screen.

(b) Sequence of colours on the screen from bottom upward:

Violet, Indigo, Blue, Green, Yellow, Orange, Red (VIBGYOR)

(c) On a green screen, only the green part of the spectrum is seen, as green. The rest of the spectrum looks dark (black).

Reason: A green surface reflects only green light and absorbs all the other colours.