Distance of ray optics as a good approximation, when the aperture is 5 mm wide and the wavelength is 600 nm is nearly :

18 m

The correct answer is option (1) : 18 m

Fresnel distance (Z)$=\frac{a^2}{\lambda}$

Here a is aperture with $\lambda $ is wavelengths of light

$Z=\frac{(5\times 10^{-3})^2}{600\times 10^{-9}}$

NA

$=\frac{25}{6}\times 10≈41.67 m$