• Support PF! Buy your school textbooks, materials and every day products Here!

Double slit dark fringes

  • #1

Homework Statement


A blue laser beam of wavelength 470nm (in air) is incident on two narrow slits separated by .2mm and produces an interference pattern on a screen located 2m away from the two slits.

Find the angular position (in degrees) of the 1st dark fringe. Can you use the small angle approximation?


Homework Equations


dsin(theta)=n(lambda)
tan(theta)= y/L



The Attempt at a Solution


I've searched all over for a formula to find the dark fringes, but all i can find is one for the light ones. the dsin(theta)=n(lambda) is used for the maxima. what formula do i use for the minima/dark fringes?
 

Answers and Replies

  • #2
rl.bhat
Homework Helper
4,433
5
For dark fringes use dsin(theta)=(n + 1/2 )(lambda)
 
  • #3
jtbell
Mentor
15,507
3,303
For two-slit interference, the minima are halfway in between the maxima.
 

Related Threads for: Double slit dark fringes

Replies
1
Views
4K
Replies
2
Views
2K
Replies
3
Views
5K
Replies
2
Views
1K
Replies
4
Views
3K
Replies
2
Views
4K
Replies
3
Views
791
Top