Question

The distance between two slits is 5 × 10-5m. if light of wavelength 500nm makes a pattern on a wall with bright fringes spaced 20mm apart, what is the distance between the slits and the wall?

Answer 1

2 m is the required answer.

GIVEN:

• Distance between two slits, d = 5 × 10^-5 m

• Wavelength of the light , λ = 500 nm = 500 × 10^-9 m = 5 × 10^-7 m

• Distance of the fringe, Y = 20 mm = 20 × 10^-3 m = 2 × 10^-2 m

TO FIND:

Distance between the slit and wall, D

FORMULA:

Y = λD/d

SOLUTION:

Y = λD/d

$2\times10^{-2} =\dfrac{5\times10^{-7}\times D}{5\times10^{-5}} \\\\2\times10^{-2} =\dfrac{10^{-7}\times D}{10^{-5}} \\\\2\times10^{-2} =10^{-2} \times D\\\\D = 2 m$

ANSWER:

The distance between the slit and wall is 2 m.

YOUNG'S DOUBLE SLIT EXPERIMENT:

• In this experiment a screen is placed at a large distance from source, in which interference pattern is observed.

• A coherent source of light is made to fall on the screen through the two slits.

• Due to constructive and destructive interference, consecutive bright and dark fringes are formed.

• This experiment supports the wave theory of light.