Photoelectric effect

Question

When light of sufficient energy hits the cathode, photoelectron are ejected towards the anode. A voltage can be applied so that no current is measured at the ammeter. This is known as stopping voltage.

--> Calculate the initial velocity of the electron if the stopping voltage us 5.13V?

Answer 1

eU = mv²/2 (U is stopping voltage, e = 1.602·10^-19 C is charge of electron , m = 9.11·10^-31kg is its mass);

v = √(2eU/m) = √(2·1.602·10^-19C·5.13V/9.11·10^-31kg) = 1.343·10⁶ m/s