Question

Two slit separated by a distance of 1 m are illuminated with red light of wavelength 6.5 into 10 to the power minus 7 m the interference fringes are observed on a screen placed 1m from the slits the distance between the third dark fringe and v dark fringe on the same side of the central maxima is

Answer 1

Answer:

Given:

Slit separation, d=1mm=1×10

−3

m

Wavelength, λ=6.5×10

−7

m

Screen distance , D=1m

To find:

Distance between 3

rd

dark fringe and 5

th

bright fringe

We know,

For distance of dark fringe, y

n

=

2d

(2n−1)λD

And, for distance of bright fringe, y

n

=

d

nλD

y

5

−y

3

=

10

−3

5×6.5×10

−7

×1

−

2×10

−3

(2×3−1)×6.5×10

−7

×1

=32.5×10

−4

−16.25×10

−4

=16.25×10

−4

m

Hence the distance between the third dark fringe and fifth bright fringe is 1.625mm