# Alternate Young double slit experiment

What will happen in Young's double slit experiment, when instead of screen I put a black screen with a hole and a second screen behind the black one. Will it still form interference pattern albeit a faint one or no interference pattern will be observed?

• In your modified experiment, the screen is replaced with a black screen that has a single circular hole?
– BMS
Apr 6 '14 at 18:29
• the screen on which interference is abserved is put behind the black one with a hole. Apr 6 '14 at 18:31
• Other YDSE questions by OP: physics.stackexchange.com/q/106662/2451 , physics.stackexchange.com/q/106666/2451 and physics.stackexchange.com/q/106969/2451 Apr 6 '14 at 18:43
• I think we'll just get a smaller and fainter interference pattern. I may be wrong.
– user42733
Apr 6 '14 at 19:38
• The question isn't clear to me. Light comes from a laser, hits a screen with a small circular hole, goes through the hole, then hits a second screen. The second screen is solid, and we observe the interference pattern on the second screen? Is that the entire setup? If so, you will see an Airy pattern. Jan 15 '15 at 22:50

## 2 Answers

If the hole in the black screen is small enough, you will not see any interference pattern, but (faint) single slit diffraction at the end. If the hole you refer to is significantly larger, it will simply mask part of the original interference pattern.

You can think of this in terms of Huygens–Fresnel principle, where the every point of light coming out of the hole becomes a source of a spherical wave. The location of this hole along the interference pattern only determines the intensity of light (and thus of the subsequent pattern).

• Will I get interference pattern greater than the size of the hole? If wave nature remains intact that is what I would expect. Apr 29 '14 at 9:03

From your description, I think you are talking about the diffraction pattern from a pinhole, and that is an Airy Disk. https://en.wikipedia.org/wiki/Airy_disk It shows a central maximum with surrounding rings which decrease in intensity as you get further from the center of the pattern.