Question

Light of wavelength 400 nm and intensity 10^-2 W/m² is incident on potassium.
(a) Estimate the time lag for the emission of photoelectrons expected classically. Assume the typical radius of an atom is
10^-10 m. Hint: Relate the light intensity to the work function for potassium.

Please explain answer clearly. (also, please explain how you got the work function for potassium)

Answer 1

Classically, we assume that the energy is transferred to the electron by the light is stored by the electron. The electron can leave the metal surface only when the energy received is equal to or greater than the work function. Here, we converted the work function in Joule(J).  

So, t = 347.75 s = 5.8 min. (approx.) is the time required to electron to come out classically. (time lag or time delay)

(Experimentally there no such time lag).