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(B) The Fresnel distance $(Z_F)$ is the distance for which ray optics is a good approximation. It is given by the formula: $Z_F = \frac{a^2}{\lambda}$

Vedclass · Accepted Answer

$40$

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(B) The Fresnel distance $(Z_F)$ is the distance for which ray optics is a good approximation. It is given by the formula: $Z_F = \frac{a^2}{\lambda}$.Given:Aperture,$a = 4 \,mm = 4 	imes 10^{-3} \,m$.Wavelength,$\lambda = 400 \,nm = 400 	imes 10^{-9} \,m$.Substituting the values into the formula:$Z_F = \frac{(4 	imes 10^{-3})^2}{400 	imes 10^{-9}}$$Z_F = \frac{16 	imes 10^{-6}}{4 	imes 10^{-7}}$$Z_F = 4 	imes 10^1 = 40 \,m$.Thus,ray optics is a good approximation for a distance of $40 \,m$.

For what distance is ray optics a good approximation when the aperture is $ 4 \,mm $ and the wavelength of light is $ 400 \,nm $ (in $\,m$)?

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