Q. Given the width of aperture = 3 mm and $\lambda$ = 500 nm. For what distance ray optics is good approximation?
A) 18 m
B) 18 mm
C) 18$\ \mathring{\mathrm{A}}$
D) 18 light years
Explanation
(a) $D_{F} = \frac{d^{2}}{\lambda}$
$D_{F} = \frac{3 \times 10^{- 3}(3 \times 10^{- 3})}{500 \times 10^{- 9}} = \frac{90}{5}m = 18m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.