Physics

Physics

Problem

Which of the following primarily determines whether electrons are emitted from a metal surface when monochromatic light is incident on it? a) Work function of the metal surface\text{Work function of the metal surface} b) Frequency of the incident light\text{Frequency of the incident light} c) Intensity of the incident light\text{Intensity of the incident light} d) Angle at which the light strikes the surface\text{Angle at which the light strikes the surface}
Intuitive explanation

The photoelectric effect depends on the energy of individual photons, not their intensity or brightness. Each photon carries energy E=hfE = hf, where ff is frequency—and only if this energy exceeds the metal's work function (the minimum energy needed to free an electron) will emission occur. Think of it as a threshold: no matter how many dim photons hit the surface, if each one lacks enough punch, nothing happens; but even a single bright photon with sufficient frequency can knock an electron loose.

Intuitive explanation

The photoelectric effect depends on the energy of individual photons, not their intensity or brightness. Each photon carries energy E=hfE = hf, where ff is frequency—and only if this energy exceeds the metal's work function (the minimum energy needed to free an electron) will emission occur. Think of it as a threshold: no matter how many dim photons hit the surface, if each one lacks enough punch, nothing happens; but even a single bright photon with sufficient frequency can knock an electron loose.

Browse the problem library