Answer to Question #131980 in Physics for Vidurjah Perananthan

Question

Tasks:
Part 1:
Light with a wavelength of 180 nm irradiates a surface of the metal Zinc with the exit work 4.0 eV. What is the speed of the released electron?

Answer 1

The energy of light will be spent on work function (4 eV) and to kinetic energy of electrons:

$$\frac{hc}{\lambda}=W+\frac{mv^2}{2},\\\space\\ v=\sqrt{\frac{2}{m}\bigg(\frac{hc}{\lambda}-W\bigg)},\\\space\\ v=\sqrt{\frac{2}{9.109\cdot10^{-32}}\bigg(\frac{6.626\cdot10^{-34}\cdot3\cdot10^8}{180\cdot10^{-9}}-4\cdot1.602\cdot10^{-19}\bigg)}=\\ =10^6\text{ m/s}$$

Very fast!