Register to reply

Optics-Diffraction of Thin Hair

by sheri1987
Tags: hair, opticsdiffraction
Share this thread:
Nov11-08, 09:10 PM
P: 48
1. The problem statement, all variables and given/known data

A human hair is illuminated with a laser and it produces a diffraction pattern on a screen 1.09 m away. If the distance from the center to the first minimum is 4.8 mm and the wavelength of the laser is 748 nm, what is the thickness of the hair? Express your answer in mm.

2. Relevant equations

wavelength = (x/m)*(w/l)

x= distance from central maximum to position of the minimum m
l= distance
w= width
m = minimum

3. The attempt at a solution

I converted 748nm to mm and 1.9m to mm and plugged in the values into the above equation and got .296 mm approximately. I set m = 1, because I thought it was asking for the 1st minimum. And x = 4.8...but the answer I got is wrong. Any help?
Phys.Org News Partner Science news on
Suddenly, the sun is eerily quiet: Where did the sunspots go?
'Moral victories' might spare you from losing again
Mammoth and mastodon behavior was less roam, more stay at home
Nov11-08, 10:53 PM
P: 363
I didn't go through your question, but I would have used the diffraction equation:


You can treat an opaque body as a "slit". See Babinet's Principle
Nov11-08, 11:30 PM
P: 1,970
In the problem you say 1.09 m and then you use 1.9 m.
With 1.09 m you get around 170 microns (or 0.17 mm) which is OK for the thickness of hair.

Nov12-08, 08:44 AM
P: 48
Optics-Diffraction of Thin Hair

Thank you very much!

Register to reply

Related Discussions
Optics / interference in thin films Introductory Physics Homework 1
Optics Thin Lens Equation Introductory Physics Homework 1
Optics - Thin Lens Formula Introductory Physics Homework 2
Can you reverse transform a thin film diffraction pattern? General Physics 6
Optics, concerning a thin film General Physics 4