Interference Patterns & Photon Paths: Exploring the Double Slit Experiment

[deadbeef]

TL;DR Summary

Question regarding photon taking longer and short path and interfering with spinnig disc that can block photon path at different moments

Hi.
As i understand in double slit experiment photon can arrive at slits through different paths (longer and shorter) and it would still show interference pattern.
My question is - if there was some path cutting device in a way of photon (on longest path after length that photon arrive at detector) (device like rotating wheel with holes) how would that affect interference pattern? Should path be clear at moment when photon is emitted? Or at moment when calculated distance to blocker (even if after detector) matches time to take longest path to blocker?

Thank you,
Reinis

 

[Nugatory]

As i understand in double slit experiment photon can arrive at slits through different paths (longer and shorter) and it would still show interference pattern.

Yes, as long as the difference in length doesn’t exceed the coherence length of the photon so that arrival at the same point on the screen at the same time is possible through either path. Increase the path length beyond that and there will be no interference. Behavior like this is why we can’t think of the photon as a small solid object following some trajectory through space.

The rotating wheel doesn’t change the general principle: if there are open paths through both slits we’ll get some amount of interference between them.

 

[deadbeef]

Yes, as long as the difference in length doesn’t exceed the coherence length of the photon

According to author (in video) he is observing interference when one path is considerably longer that other path. Is there some error in his experiment?

 

[Nugatory]

According to author (in video) he is observing interference when one path is considerably longer that other path. Is there some error in his experiment?

I haven’t watched the whole thing, just the few seconds you excerpted…. But from that I would expect that “considerably longer” is still less than the coherence time of the photons, so no mistake.