Revision: Electrons and Photons Physics HSC Science (General) 12th Standard Board Exam Maharashtra State Board

It is a phenomenon where light falling on a material (usually a metal) causes it to emit electrons, generally called photoelectrons.

The emission of electrons from a metal surface when electromagnetic radiation of sufficiently high frequency falls on it. This phenomenon is called the photoelectric effect.

Electrons emitted from the metal during photoelectric emission are called photoelectrons.

The minimum frequency of incident radiation required to just cause photoelectric emission from a given metal is called the threshold frequency.

• Photoelectric emission was discovered in 1887 by Heinrich Hertz.
• Hertz made this observation during electromagnetic wave experiments.
• High-voltage sparks across the detector loop were enhanced when the emitter plate was illuminated by ultraviolet light from an arc lamp.
• Light shining on the metal surface facilitated the escape of free, charged particles.
• These free, charged particles are electrons.
• Electrons near the metal surface absorb energy from incident radiation.
• If the absorbed energy is sufficient, electrons overcome the attraction of positive ions in the material.
• The electrons then escape from the metal surface into the surrounding space.