3. An element that is malleable is A. Easily shaped B. Very hard C. Difficult to pour D. Very dense

Determine the expected diffraction angle for the first-order reflection from the (310) set of planes for bcc chromium when monochromatic radiation of wavelength 0.0735 nm is used. the atomic radius for cr is 0.1249 nm.

Can someone explain to me how to do this problem ?

What is relative velocity? in which condition is relative velocity known by adding the velocity of the first body and that of the second body