Question

Light of wavelength `600 nm` is incident on an aperture of size `2 mm`. Calculate the distance light can travel before its spread is more than the size of aperture.

Answer 1

Here, `lambda = 600 nm = 6 xx 10^(-7)m`,
`a = 2mm = 2 xx 10^(-3)m`
The required distance is Fresnel distance
`Z_(F) = (a^(2))/(lambda) = (2 xx 10^(-3))^(2)/(6 xx 10^(-7)) = 6.67 m`