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**Physics, Astronomy & Cosmology / Re: What happens with the double slit if the slits are at 90 degrees ?**

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**Today**at 05:05:17 »

The circular diffraction pattern was new to me, and very neat...

Back to the OP: In those videos, the light source was a green laser, which has a very narrow beamwidth.

If you had 2 slits at right angles to each other, and you illuminated one 1 slit perpendicularly, almost no light would go through the second slit.

A diffraction grating has a very different diffraction pattern than a slit - a grating produces light at a series of angles, where the grating spacing corresponds to multiples of the light wavelength. Some of these multiples can produce very wide angles of diffraction; with a slit, energy at large angles is very much lower.

See: https://en.wikipedia.org/wiki/Diffraction_grating

Back to the OP: In those videos, the light source was a green laser, which has a very narrow beamwidth.

If you had 2 slits at right angles to each other, and you illuminated one 1 slit perpendicularly, almost no light would go through the second slit.

A diffraction grating has a very different diffraction pattern than a slit - a grating produces light at a series of angles, where the grating spacing corresponds to multiples of the light wavelength. Some of these multiples can produce very wide angles of diffraction; with a slit, energy at large angles is very much lower.

See: https://en.wikipedia.org/wiki/Diffraction_grating