What is the period of the pattern from the double slit experiment? It varies along the pattern right? Namely I'm confused because when considering two point sources (See: Period of Interference Pattern on a Substrate) this should be like the double slit, at least along the x-axis. That being said, it gives the period as $\frac{\lambda}{2 \sin(\theta)}$ at the origin. I don't know how to calculate the period in the double slit experiment though, so I don't know if this agrees.
Asked
Active
Viewed 382 times
2 Answers
1
Calculate the distance between the center and the first maximum. The position of the first maximum is easily obtained by considering path length and constructive interference, and making a small angle approximation. Yo should really be able to do this before answering this question.
lionelbrits
- 9,355
-
Why would you multiply by two? – Nov 21 '13 at 19:49
-
To get twice the answer, of course. Heh. I was thinking about minima when I wrote that. – lionelbrits Nov 21 '13 at 20:44
-
So then, how do I recover the same period? Or are they actually different phenomena? I'm really confused. – Nov 21 '13 at 20:48
-
Could it be that looking at the first points period is an average the way we are doing it? – Nov 21 '13 at 21:05
-
Well, I'm a bit confused why your formula has $\theta$ in it if it is supposed to be at the origin. – lionelbrits Nov 21 '13 at 23:43
-
Haha I just realized that. My bad. – Nov 22 '13 at 09:58
0
On axis in the 1D small angle approximation the spacing is constant. When you have point sources and you go off axis (in the direction perpendicular to the line connecting the two points) that may not be true - it is also not true when the small angle approximation breaks down (higher order fringes).
You should be able to find details and diagrams in any decent text book on optics.
Floris
- 118,905