Question

Explain Hertz and Lenard's observation of the photoelectric effect.

Answer 1

Heinrich Hertz's observation,

1. In 1887 Heinrich Hertz observed that some electrons near the surface are seen to absorb energy from the incident radiation when light falls on a metal surface.
2. The attraction of the positive ions in the material of the surface is overcome by this.
3. The electrons escape from the surface of the metal into the surrounding space after gaining sufficient energy from the incident light.

Lenard's observation,

1. In 1902, Lenard observed that with the increase in the frequency of radiation used there is an increase in the kinetic energy of electrons emitted too.
2. This could not be explained as Maxwell’s electromagnetic theory predicted that kinetic energy should only depend upon light intensity.
3. Kinetic Energy should not be dependent on Frequency.