Question

When a monochromatic light passes through a slit 0.2 mm wide and falls on a screen 3.5 m away, the first minimum of the diffraction pattern is 9.1 mm from the centre of the central maximum. The wavelength of the light is ______.

Options

• 2600 A

• 4000 A

• 4300 A

• 5200 A

Answer 1

When a monochromatic light passes through a slit 0.2 mm wide and falls on a screen 3.5 m away, the first minimum of the diffraction pattern is 9.1 mm from the centre of the central maximum. The wavelength of the light is 5200 A.

Explanation:

`X_m=(mDlamda)/a`

`lamda = (axxX_m)/(mD) = ((2xx10^-4)(9.1xx10^-3))/3.5`

`=(18.2xx2)/7xx10^-7`

`=5.2xx10^-7m=5200A`