Question

Light of wavelength 600nm is incident on an aperture of size 2 nm . 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

Answer: (B)

6.67 m

Answer 2

The distance upto which light can travel is

Fresnel distance

$z_{F} = \frac{d^{2}}{\lambda} = \frac{(2 \times 10^{- 3})^{2}}{600 \times 10^{- 9}} = 6.67m$