Light from a HeNe laser (632.8 nm wavelength) is directed upon a straightened strand of human hair, 7.5 m from the wall. By examining the diffraction pattern produced on the wall, the diameter of the hair can be determined (the diffraction pattern thus produced has minima in the same locations as if the hair were a slit of the same width in an otherwise opaque barrier). If the central diffraction maximum is measured to be 14.6 cm wide, what is the diameter of the hair?
A) 65 µm
B) 32.5 µm
C) 43.3 µm
D) 86.6 µm

Question

Quizplus · Accepted Answer

The diameter of the hair can be determined using the formula:d = (λL) / wwhere:d is the diameter of the hairλ is the wavelength of the lightL is the distance from the hair to the wallw is the width of the central diffraction maximumPlugging in the given values, we get:d = (632.8 nm * 7.5 m) / 0.146 m = 32.5 µmTherefore, the diameter of the hair is 32.5 µm, which corresponds to choice A.

Light from a HeNe Laser (632