Dispersion by diffraction grating

  • #1

Homework Statement



White light containing wavelengths from 396 nm to 756 nm falls on a grating with 7300 lines/cm. How wide is the first-order spectrum on a screen 2.15 m away?

Homework Equations


y=m*L*wavelenth/(d)


The Attempt at a Solution


using the equation I have found y1 to be 62.149 and y2 118.635. I took the difference of the two which gave me 56.486 cm, but that is wrong for some reason. Please help.
 

Answers and Replies

  • #2
49
2
Are you sure of that that's the equation for diffraction? Checking the units, it's quite inconsistent... Check the equation again...
 
  • #3
That's the equation I'm used to. If we assume that the angle is small then sintheta=y/L
dsintheta=m*wavelength
d(y/L)=m*wavelength
m*wavelength*L/(d)=y ? I don't know what's wrong with the equation. For the units I coverted everything to cm because 1/7300=d in cm.
 
  • #4
Please help, I only have a couple of hours left.
 
  • #5
49
2
I got 56.502 cm, using the equation. we seem to get the same answer.
 
Last edited:

Related Threads on Dispersion by diffraction grating

  • Last Post
Replies
3
Views
864
Replies
3
Views
763
Replies
2
Views
3K
Replies
10
Views
3K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
3
Views
1K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
4
Views
2K
Top