Interference, Diffraction, Diffraction Grading

[Kirstin]

Can someone explain to me how to compute the different items concerning interference, diffraction and diffraction grading. I an not able to understand my physics book.

[swansont]

Can someone explain to me how to compute the different items concerning interference, diffraction and diffraction grading. I an not able to understand my physics book.

If you have two waves and combine them, they will interfere. If the peaks line up, it's constructive interference. This will also happen if one of the waves takes a path that is longer or shorter by a full wavelength, so the peaks again line up.

You will get destructive interference if the path difference is half of a wavelength - the peak of one wave cancels with the trough of the other.

The equations in your textbook are just applying those conditions to the geometry of the situation.