Question

What is the velocity (u ) of an electron (in km/s) ejected from a metal (W = 3.57 eV ) using a photon of light with a wavelength of 329 nm? (1 eV = 1.602×10–19 J; h = 6.626 ×10–34 J.s; me = 9.109×10–31 kg) (keep 3 sig. fig. in your final anser and do NOT use scientific notation.)

Answer 1

Well you know

\[hf = W + E_{k}\]

Where E is the kinetic energy of the electron

So, you will have \[ v = \sqrt{2(hf - W)/m}\]

You, can get the frequency of the light by noting the relationship \[c = \lambda f\] and solving for f.

Hope this helps :)