일반물리학 2 — Diffraction: Problem 39

39 (a) How far from grains of red sand must you be to position yourself just at the limit of resolving the grains if your pupil diameter is $1.8 \text{ mm}$, the grains are spherical with radius $50 \mu\text{m}$, and the light from the grains has wavelength $650 \text{nm}$? (b) If the grains were blue and the light from them had wavelength $400 \text{nm}$, would the answer to (a) be larger or smaller?