Estimate the wavelength of a 30 keV electron.
p = h/λ
E = hf
The Attempt at a Solution
The electron has 30 keV of mass-energy.
As it is acting as a particle-wave, E = hf, so f = E/h = 30,000x1.6x10^-19/6.3X10^-34 = 7.619x10^18 Hz
Now, v = fλ, so λ = v/f, but this is where I run into a problem, as I'm not told what speed the electron is travelling at - do I assume speed of light, or is there some other way?