Question

FULL SCREEN PRINTER VERSION BACK NEXT Question 2 How fast must an electron move to have a kinetic energy equal to the photon energy of light at wavelength 620 nm? The mass of an electron is 9.109 x 10 kg. Number Units the tolerance is +/-5%

Answer 1

Here,

let the electon velocity is v

for the kinetic energy

m * c^2 - m0 * c^2 = kinetic energy = h * c/wavelength

9.11 *10^-31 * (3 *10^8)^2/sqrt(1 - (v/(3*10^8))^2) - 9.11 *10^-31 * (3 *10^8)^2 = 6.626 *10^-34 * 3 *10^8/(620 *10^-9)

solving for v

v = 8.39 *10^5 m/s

the speed of the electron is 8.39 *10⁵ m/s