# In the Double Slit Experiment, what type of wave are we talking about?

I was learning about the double slit experiment and simple explanation is that there is wave interference. Although I do not quite understand the wave bit. We know that light is a wave.

But in the image of the wave interference we see something like two ripples (in water) that interfere.

I couldn't understand that how could a sine wave, pass through a slit and then suddenly become ripples.

P.S. If we imagine a sine wave passing through a slit, we (or probably I) should expect a sine wave, because the front side of the sine wave is one-dimensional and that passing through a slit just a wee wide, shouldn't change anything.

• Are you asking how the light is able to spread out as it exits the slit? Commented Aug 31, 2020 at 17:50
• The lines you see represent the maxima of the sine probability waves. Commented Aug 31, 2020 at 17:59
• @Shubhkarman Sandhu those curves escaping the slit represent the wavefront not the sine wave itself. Commented Aug 31, 2020 at 18:21
• The cross-section of a series of ripples is a sine wave. This is true whether the cross-section is longitudinal or radial and the ripples are in light, water or anything else. Commented Aug 31, 2020 at 18:54
• The probability of finding the photon at a place when measuring is related to the (operator-)weighted inner product of the photon's wave function, which is a complex number at each position, with dynamics as the Schrödinger equation tells. I don't know if the first picture is supposed to show the wave function or the electric field.
– Emil
Commented Sep 1, 2020 at 5:54