1. The problem statement, all variables and given/known data Find the energy (in joules), rest mass (kg), speed (m/s), wavelength (m), and momentum (kgm/s) of a 2.2 eV electron. I'm having trouble finding the speed of the electron; once I have that I can find the wavelength and momentum. E = energy p = momentum h = Planck's constant (6.63 x 10-34 Js) c = the speed of light (3.0 x 108 m/s) λ = wavelength 2. Relevant equations 1 eV = 1.60 x 10-19 J Etotal = Ek + Erest E = hc/λ p = h/λ 3. The attempt at a solution Energy of electron in joules: 2.2 eV = 3.52 x 10-19 J Rest mass of an electron: 9.11 x 10-31 kg ****(Is this a correct answer or do I need to calculate rest mass?) Speed of electron: I tried this equation: Etotal = Ek + Erest Ek = Etotal - Erest but it doesn't work because the total energy given for the electron is less than the rest energy calculated... I'm not sure what equation other equation I can use. Also, I don't know if relativity must be taken into account if the electron's speed is close to the speed of light? Thank you!