For what distance is ray optics a good approximation when the aperture is 4mm wide and the wavelength is 500 nm ?

For what distance is ray optics a good approximation when the aperture

1.	For what distance is ray optics a good approximation when the aperture is 4mm wide and the wavelength is 500 nm ?
Answer» 32m 64m 16m 8m Solution :Fresnel.s distance `Z_(F)=(a^(2))/(lamda)=((4mm)^(2))/((500nm))=((4XX10^(-3)m)^(2))/((500xx10^(-9)m))=32m`.

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For what distance is ray optics a good approximation when the aperture is 4mm wide and the wavelength is 500 nm ?

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