일반물리학 2 — Diffraction: Problem 45

45 A 0.20 mm wide slit is illuminated by light of wavelength 420 nm. Consider a point P on a viewing screen on which the diffraction pattern of the slit is viewed; the point is at 30° from the central axis of the slit. What is the phase difference between the Huygens wavelets arriving at point P from the top and midpoint of the slit? (Hint: See Eq. 36-4.)