Question

In the biprism experiment, the fringe width is 0.4 mm. What is the distance between the 4^th dark band and the 6^th bright band on the same side? 

Options

• 0.75 mm

• 0.5 mm

• 1 mm

• 1.5 mm

Answer 1

1 mm

Explanation:

Distance of n^th bright band from the centre is given by

x_n = nX

Where X is the fringe width.

Distance of n^th dark band from the centre is given by

`x_n^' = (n - 1/2)X`

Distance of 6^th bright band X₆ = 6X

Distance of 4^th dark band `X_4^'` = 3.5X

∴ `X_6 - X_4^' = 2.5 X = 2.5 xx 0.4 = 1` mm