Question

In Young's experiment for the interference of light, the separation between the silts is d and the distance of the screen from the slits is D. If D is increased by 0.6% and d is decreased by 0.2%, then for the light of a given wavelength, which one of the following is true?

"The fringe width  ____________."

विकल्प

• increases by 0.8%

• decreases by 0.8%

• increases by 0.2%

• decreases by 0.2%

Answer 1

"The fringe width increases by 0.8%."

Explanation:

`"W" = lambda"D"/"d"`

`therefore  %  "change in fringe width,"`

`(Delta"W")/"W" xx 100 = (Delta"D")/"D" xx 100 - (Delta "d")/"d" xx 100`

`= 0.6 - (-0.2) `   ......[Here, `(Delta"d")/"d"` is negative as d is decreased]

= 0.8 %

Positive value indicates increase in fringe width.

∴ Fringe width increases by 0.8 %.