A monochromatic light source of power 5mW emits `8 xx 10^(15)` photons per second. This light ejects photo electrons from a metal surface. The stopping potential for this set up is 2V. Calculate the work function of the metal.

Explanation

Given `W_0 = hv - ev_0 `
`= 5 xx 10^(-3) / 8 xx 10^(15) - 1.6 xx 10^(-19) xx 2 `
` = 6.25 xx 10^(-19) - 3.2 xx 10^(-19) `
`= 3.05 xx 10^(-19)`
` 3.05 xx 10^(-19) / 1.6 xx 10^(-15) = 1.906 eV.`