Question

In young's double slit experiment, if monochromatic light is replaced by by white light:

• A. All bright fringes become white.
• B. All bright fringes have colours between violet and red.
• C. Only the central fringe is white, all other fringes are coloured.
• D. No fringes are observed.

Answer 1

Answer: (A)

All bright fringes become white.

In young's double slit experiment, if white light is used in place of monochromatic light, then the central fringe is white and some coloured fringes around the central fringe are formed.
Since ${\beta }_{red}>{\beta }_{violet}$ etc. the bright finger of violet colour forms first and that of the red forms later.
It may be noted that, the inner edge of the dark fringe is red, while the outer edge is violet. Similarly , the inner edge of the bright fringe is violet and the outer edge is red.