Compare the wavelengths of an electron (mass=9.11x10^-31 kg) and a proton, (mass=1.67x10^-27 kg) each having (a) a speed of 8.38x10^6 m/s and (b) a kinetic energy of 1.39x 10^-15 J.

I am trying to use de Broglie's wavelength formula and for part (a) I am suppose to find the wavelength using the formula and the masses and speed but for part (b), I can't figure out if I am suppose to use both the speed, the energy, and the masses, or just the energy and the masses.

Question

Compare the wavelengths of an electron (mass=9.11x10^-31 kg) and a proton, (mass=1.67x10^-27 kg) each having (a) a speed of 8.38x10^6 m/s and  (b) a kinetic energy of 1.39x 10^-15 J. 

I am trying to use de Broglie's wavelength formula and for part (a) I am suppose to find the wavelength using the formula and the masses and speed but for part (b), I can't figure out if I am suppose to use both the speed, the energy, and the masses, or just the energy and the masses.

aaronq · Answer

For a) use debroglie's with the speed first, then separately for b), find the speed with the energy given, then the wavelength with debroglie's.