Problem 17.69 One day, after pulling down your window shade, you notice that sun
ID: 1444928 • Letter: P
Question
Problem 17.69 One day, after pulling down your window shade, you notice that sunlight is passing through a pinhole in the shade and making a small patch of light on the far wall. Having recently studied optics in your physics class, you're not too surprised to see that the patch of light seems to be a circular diffraction pattern. It appears that the central maximum is about 6 cm across, and you estimate that the distance from the window shade to the wall is about 5 m .
Knowing that the average wavelength of sunlight is about 500 nm, estimate the diameter of the pinhole.
Explanation / Answer
sintheta = 1.22 * lambda/d
sin theta = tan theta = y/D
y/D = 1.22 * lambda/d
d = 1.22 * lambda *D/y
given = y = 6cm = 6 x 10^-2 m
D = 5m
d = 5.08 x 10^-5 m