Question

In Young's double slit experiment green light is incident on the two slits. The interference pattern is observed on a screen. Which one of the following changes would cause the observed fringes to be more closely spaced?

पर्याय

• Moving the screen away from the slits

• Using blue light instead of green light

• Using red light instead of green light

• Reducing the separation between the slits

Answer 1

Using blue light instead of green light

Explanation:

The distance between the fringes or the fringe width is given by

β = `("D"λ)/"d"`

where, λ = wavelength of light used,

D = distance of slits from screen

and d = separation between slits.

So, to reduce the space between fringes

(i) D should be reduced

(ii) d should be increased

(iii) λ should be reduced

As blue light has shorter wavelength than green light. So, by using blue light instead of green light, the fringes become more closely.