Dear Suraj Kumar Yadav ,

just have a look at the Bragg law: lambda = 2*d*sin(theta)

and the parameters involved there:

sin(theta) < 1, d ~ atomic _distance

---> lambda = 2*d*sin(theta) < 2*atomic_distance

You may also have a look at the middle of the 2theta scale (~60°) which will give: sin(theta) ~ sin(30°) = 1/2.

You will end up here with: lambda ~ 1*atomic_distance

Best regards

G.M.

That is because the interference that causes diffraction occurs when the wavelength and the interfering thing is similar in distance. When the distance is spaced such that waves come out (reflect, transmit etc.) in phase, this will counter the diffuse scattering and other effects that generally occur, but only for a certain subset of the incident waves which is why the characteristic pattern of repeating dots occur.

Hope this helps a little!

You are right, Steven Van Petegem ,

you can go much smaller in lambda compared to the atomic distance.

This condition (lambda lambda < (2/n) * atomic_distance

But for the other way round (lambda >> atomic_distance) the Bragg law will not work.