Comment by Balgair

I'm sorry what?

What do you mean by diffraction here? Are you talking about the bokeh?

The laser isn't interacting with any other elements than the air before it makes the gradient sheet light up. And the permisivity of the air is about the same as vacuum here.

Like, the grating is going to show a diffraction pattern similar to any pinhole aperture source [0] because of the 'half cancellations' they kinda explain, but not all that in depth.

But since there are no elements in the path yet, the only conclusion we can make is that of Feynman's - that the light is in fact taking all possible paths and then cancelling out to make the laser light we normally experience.

What am I missing? To me this demo is like mind boggling as it shows that the wave model is the correct one even with a laser.

[0] https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2F...

Something like (a) above, though I'm not confident that this is really showing that exactly.