Optics Question 138
Question: In Young’s double slit experiment, if monochromatic light is replaced by white light
[AIIMS 2001; Kerala PET 2000; KCET 2004]
Options:
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
Show Answer
Answer:
Correct Answer: C
Solution:
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 fringe 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.
