A small potassium foil is placed (perpendicular to the direction of incidence of light) a distance
Channel: Doubtnut
Date: 2020-04-12

A small potassium foil is placed (perpendicular to the direction of incidence of light) a distance `r( =0.5 m)` from a point light source whose output power `P_(0)` is `1.0W`. Assuming wave nature of light how long would it take for the foil to soak up enough energy `(=1.8eV)` from the beam to eject an electron? Assume that the ejected photoelectron collected its energy from a circular area of the foil whose radius eqals the radius of a potassium atom `(1.3xx10^(-10)m)`