Question

In Young's double slit experiment, the fringes are displaced by a distance x when a glass plate of refractive index 1.5 is introduced in the path of one of the beams. When this plate is replaced by another plate of the same thickness, the shift of fringes is (3/2) x. The refractive index of the second plate is(a) 1.75(b) 1.50(c) 1.25(d) 1.00

Answer 1

(c) 1.25 is correct answer.

Answer 2

Answer:

A) 1.75

Explanation:

Refractive index = 1.5 (given)

As per young's double slit experiment -

Fringe shift x = D/d(u-1)t -- (1)

Where D is the distance of slit from the screen

d is the distance between two slits

t is the thickness of glass plate

Thus, 3x/2 = D'(u-1)t/d -- (2)

Dividing equation 2 by 1

3/2 = (u'-1)/(u-1)

= 3u-3 = 2u-2

3×1.5-3 = 2u"-2 (Given u = 1.5)

4.5-1 = 2u'

3.5 = 2u

u = 3.5/2

u = 1.75

Thus, the refractive index of the second plate is 1.75