The width of an aperture is 4 mm and wavelength of light illuminating it is 600 nm. Find the distance up to which ray optics is valid.

Explanation

To find the distance up to which ray optics is valid, we will calculate the Fresnel distance using the formula:

\[ D_F = \frac{a^2}{\lambda} \]

where:
- \( D_F \) is the Fresnel distance,
- \( a \) is the width of the aperture,
- \( \lambda \) is the wavelength of light.
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