what is braggs law and wat r its primary applicatons?

Answer 1

Per the reference, Bragg's law defines key characteristics of the pattern produced by X-ray diffraction by a crystalline material. These characteristics "allow us to calculate details about the crystal structure, or if the crystal structure is known, to determine the wavelength of the x-rays incident upon the crystal."

Answer 2

Braggs law...

the answer is it is useful for x-ray diffraction. (that is the only case that i have encountered it... and it is the only place that i have heard of it being used)

Bragg set out with a crazy idea that if you took a crystal you could assume that each atomic layer was a semipermiable membrain, so that when you shown an xray on it you would get relflection off of each atomic layer. Now this means that there would be interfeirence between the reflected parts of each layer. subsaquently they almost always cancel out. i SAID almost always... it turns out that there is an exact angle such that the reflections all add to each other and you get a good clean reflection (defraction rather)

Now that is for a perfect crystal. In reality no crystal is quite perfert, they are filled with twist and breaks. So if you measure the allowed angles for the xray diffraction on a crystal depending on how few angles are allowed you can see how good your crystal is (very useful in mateiral physics)

Any who as I said Bragg came up with this crazy idea... and then he proved it... He did the experiments. The actual reason for why it works is much more complicated, but what he came up with works, and works well.