Question

distance between 8th maxima and 4th minima is 1 mm . find the fringes width​

Answer 1

Explanation:

Position of nth bright fringe from central maxima x

n

1

=

d

n

1

λD

here n

1

=5

∴x

n

1

=

d

5λD

Position of nth dark fringe from central maxima.

x

n

=

2d

(2n−1)λD

, Here n=3

x

n

=

2

5

d

λD

x

n

1

−x

n

=

d

2.5λD

=2.5β

Given β=0.4mm

⇒x

n

1

−x

n

=1mm