1. The problem statement, all variables and given/known data The X-ray intensity distribution function for an X-ray lamp is given on the figure. What is the maximum velocity of the electrons? What is the potential difference under which the lamp is operating? Figure: http://imgur.com/01kCBc8 2. Relevant equations Kmax = 0.5m(vmax)^2 Kmax = hf - work function λ = c/f c = speed of light = 3 x 10^8 m/s Peak wavelength (from the figure) = 3.5 x 10^-9 m h = Planck's constant = 6.63 x 10^-34 m = mass of electron = 9.11 x 10^-31 3. The attempt at a solution Doubt I'm starting at the right place. 0.5mv^2 = hf (work function??) 0.5mv^2 = h(c/λ) v = sqrt [2h(c/λ)/m] v = 1.1 x 10^7 m/s Given answer is 1.5 x 10^7 m/s As for the potential difference, I have no idea how to calculate it.