Dual Nature of Radiation and Matter | Class 12 Physics Notes
By ConceptScroll Team · Published on 17 July 2026 · 2 min read
Dual Nature of Radiation and Matter – this guide gives you a concise, exam-ready overview of Dual Nature of Radiation and Matter from Class 12 Physics, written by ConceptScroll editors and reviewed against the latest NCERT textbook.
11.2 ELECTRON EMISSION
Metals contain free electrons responsible for electrical conductivity. However, these electrons cannot normally escape the metal surface because when an electron attempts to leave, the metal surface becomes positively charged and pulls the electron back due to electrostatic attraction. Thus, electrons are held inside the metal by attractive forces from the positive ions. To escape, an electron must gain sufficient energy to overcome this attractive pull. The minimum energy required for an electron to escape the metal surface is called the work function (φ₀), measured in electron volts (eV). One electron volt is the energy gained by an electron accelerated through a potential difference of 1 volt (1 eV = 1.602 × 10^-19 J). The work function depends on the metal's properties and surface nature. Electron emission can be induced by: (i) Thermionic emission – heating the metal to provide thermal energy to electrons; (ii) Field emission – applying a very strong electric field (~10^8 V/m) to pull electrons out; (iii) Photoelectric emission – illuminating the metal with light of suitable frequency to eject electrons (photoelectrons).
🔗 Connection: Prepares for detailed study of the photoelectric effect and its experimental investigation.
Frequently asked questions
The minimum energy required for the electron emission from the metal surface can be supplied to the free electrons by which of the following physical processes?
All the above
When photons of energy, h v fall on an aluminium plate having work function ø o , photoelectrons of maximum kinetic energy K are ejected. If the frequency of radiation is doubled, the maximum kinetic energy of the ejected photoelectrons will be
K + h v
In the Davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by
increasing the potential difference between the anode and the filament
With the increase in the intensity of incident radiation, the
photoelectric current increases
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