Register to reply 
OpticsDiffraction of Thin Hair 
Share this thread: 
#1
Nov1108, 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? 


#2
Nov1108, 10:53 PM

P: 363

I didn't go through your question, but I would have used the diffraction equation:
[tex]d\sin\theta=m\lambda[/tex] You can treat an opaque body as a "slit". See Babinet's Principle 


#3
Nov1108, 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. 


#4
Nov1208, 08:44 AM

P: 48

OpticsDiffraction 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 