Light from a HeNe Laser (632 $7.5 \mathrm{~m}$ From the Wall $14.6 \mathrm{~cm}$

Multiple Choice

Light from a HeNe laser (632.8 nm wavelength) is directed upon a straightened strand of human hair, $7.5 \mathrm{~m}$ 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 $14.6 \mathrm{~cm}$ wide, what is the diameter of the hair?

A) $65 \mu \mathrm{m}$
B) $86.6 \mu \mathrm{m}$
C) $43.3 \mu \mathrm{m}$
D) $32.5 \mu \mathrm{m}$