Physics

Physics

Problem

Light of threshold frequency 5.5×1014 Hz5.5\times10^{14}\,\text{Hz} just causes photo-emission from a metal. Calculate the work function of the metal in electron-volt. (Take h=6.63×10−34 J sh=6.63\times10^{-34}\,\text{J\,s}, e=1.6×10−19 Ce=1.6\times10^{-19}\,\text{C}.)
Intuitive explanation

The photoelectric effect hinges on the idea that light energy must overcome a barrier—the work function—before electrons escape. At the threshold frequency, the photon energy exactly equals the work function with no energy left over for the electron's motion. Use E=hfE = h f to find the energy in joules, then convert to electron-volts by dividing by the elementary charge.

Intuitive explanation

The photoelectric effect hinges on the idea that light energy must overcome a barrier—the work function—before electrons escape. At the threshold frequency, the photon energy exactly equals the work function with no energy left over for the electron's motion. Use E=hfE = h f to find the energy in joules, then convert to electron-volts by dividing by the elementary charge.

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