If a metal sheet containing a tiny hole is heated (without damaging it) and therefore expands, what happens to the angular location of the first-order diffraction maximum?
A) It doesn't change.
B) It moves toward the centerline.
C) It moves away from the centerline.

Question

Quizplus · Accepted Answer

When the metal sheet expands, the tiny hole also expands, increasing its diameter. According to the formula for diffraction maxima, $d \sin \theta = m\lambda$ (where $d$ is the diameter of the hole, $\theta$ is the angle to the maximum, $m$ is the order of the maximum, and $\lambda$ is the wavelength of the light), an increase in $d$ results in a decrease in $\sin \theta$ for the first-order maximum ($m = 1$), meaning $\theta$ decreases. Therefore, the first-order diffraction maximum moves toward the centerline.

If a Metal Sheet Containing a Tiny Hole Is Heated