Question

Light of wavelength 600 nm is incident on an aperture of size 2 mm. The distance upto which light can travel such that its spread is less than the size of the aperture is:

• A. 12.13 m
• B. 6.67 m
• C. 3.33 m
• D. 2.19 m

Answer 1

The correct option is B 6.67 m

Given:

Aperture Width, $a=2mm=2\times {10}^{-3}mm$

The distance upto which light can travel is Fresnel distance, $Z_F=\frac{a^2}{\lambda }=\frac{(2\times {10}^{-3}{)}^2}{600\times {10}^{-9}}=6.67m$