Question

Under appropriate conditions, molybdenum emits X rays that have a characteristis wavelength of 0.711 Angstrom.
These X rays are used in diffraction experiments to dtermine the structures of molecules. How fast would an electron have to be moving in order to have the same wavelength as these X rays?

The answer is V= 1.02x10^7 m/s

My question: At first I tried converting Angstroms to Meters and then using the formula V= C/Lambda, in which C is 3x10^7m/s and Lambda would be the Angstroms I coverted, however the m's x-out and then I would only have s....so I need some help!

Answer 1

Use the deBroglie hypothesis

wavelength= h/mv

solve for v.

By the way, the speed of light in free space is 3*10⁸, not 10⁷ m/s