# Cases of Double slit experiment [duplicate]

I'm a high schooler, and I want to clarify what I know about the double-slit experiment. I broke down the double slit experiment into 4 categories: particle w/one & two slit, and wave w/one & two slit.

If we have a single slit w/ waves, they do not interfere, so they create one bright spot on the screen. But if we have a double slit w/ waves, the waves diffract and interfere constructively and destructively to create a band of dark and bright spots on the screen.

On the other hand, if we have one slit w/particles (i.e. electrons), there's just a single bright spot on the screen. And if we have a double slit w/particle, there's two bright spots on the screen. However, light has a wave-particle duality, so if we have a one slit w/light, it interferes with itself (The photons go through both slits and interfere with each other?), and if we have a double-slit, the light behaves like a wave, and thus also interferes with itself?

My question: Am I correct on the above information, and if so, how can a particle interfere with itself? Does it split in half?

## marked as duplicate by stafusa, sammy gerbil, Kyle Kanos, heather, glSJul 8 '18 at 14:24

• If you have a single slit with waves, interference can happen if the single slit is wider than a wavelength. en.wikipedia.org/wiki/Diffraction#Single-slit_diffraction – probably_someone Jun 28 '18 at 16:21
• Re, "single slit...waves...one bright spot." Nope. Not if the slit is the same size as the slits that make the double-slit experiment work. Light passing close to the edge of the slit is diffracted (i.e., spread out). If the slit is narrow enough, that means, most of the light passing through it is diffracted. The dark and light bands produced by the double slit experiment occur in the space where the diffraction patterns from the two individual slits overlap. – Solomon Slow Jun 28 '18 at 17:35
• "If we have a single slit w/ waves, they do not interfere" That is incorrect. "If we have one slit w/particles (i.e. electrons), there's just a single bright spot on the screen" That is only correct if the electron momentum is large enough. Electrons show interference (any number of slits) just like photons. "And if we have a double slit w/particle, there's two bright spots on the screen" Same comment. You should get your facts straight first. – my2cts Jun 28 '18 at 23:50

What causes the interference is the double slit if you have one slit it will not be any interference no matter what you "shoot" at it.

So the interesting stuff happens only with the double slit, what happens is that the double slit makes the "projectile" act as a wave the projectile can be a photon, electron, proton, etc.

This experiment lets us know that particles are not really "solid" particles because the double slit makes them interact as waves i picture this particles like a "hard to divide" cloud so when you shoot that cloud to the double slit lets say 90% of it enters through one slit and 10% of it enters through the other slit and there is where the interaction happens but since the cloud is hard to divide the 10% will follow the 90% like a cat in which its head enters through one slit and its tail enters through the other but then because the head has more "energy" the tail follows the head's path so in the end both parts pass through the same slit but the tail entered the other slit and interacted with the head but then it followed the head i hope you can understand it with this analogy.

So the particle can interact with itself because the double slit area is covered by the particle's cloud or volume of influence if you want.

• This is not true. Single-slit interference definitely happens, as long as your single slit is wider than the wavelength. en.wikipedia.org/wiki/Diffraction#Single-slit_diffraction – probably_someone Jun 28 '18 at 15:51
• Yeah but that is not relevant to what the user is asking – Adou Jun 28 '18 at 16:20
• It is, though, since it's one of the premises that they're using to ask their question. "If we have a single slit w/waves, they do not interfere..." – probably_someone Jun 28 '18 at 16:22
• That was used to introduce the question, but yes i think we have to wait for the asker to clarify what he wanted to know – Adou Jun 28 '18 at 16:27
• No, you don't. I just showed you that you don't. You can get an interference pattern from a single slit. – probably_someone Jun 28 '18 at 16:49