CBSE Class 12 Physics Dual Nature Of Matter And Radiation Notes Set B

7. DUAL NATURE OF MATTER & RADIATION

GIST

1. The elementary particle in an atom having negative charge of magnitude 1.6 x 10^-19 C and mass of 9.1 x 10^-19 kg is called electron.

2. There are four types of electron emission, namely, Thermionic Emission, Photoelectric Emission, Field Emission and secondary emission.

3. The minimum energy required by an electron to escape from the metal surface is called work function.

5. Work function is conveniently expressed in electron volts ( e V ).

6. One electron volt is the energy gained or lost by an electron while passing through a potential difference of one volt.

7. The phenomenon of emission of electrons from metal surface when suitable high frequency radiation incidents on it is called photoelectric effect. The electrons thus emitted are called photo electrons.

8. The electric current in the circuit constituting the photo electrons is called photoelectric current. It depends on the intensity of incident radiation, potential difference applied between the two electrodes and the nature of the material.

9. The minimum negative voltage required to stop completely the photo electric current is called stopping potential.

10The frequency of incident radiation below which no photo electric effect takes place is called threshold frequency.

Laws of photoelectric effect:

1. The photoelectric emission is an instantaneous process.

2. For a given metal and frequency of radiation the photoelectric current is directly proportional to the intensity of incident radiation.

3. For a given metal if the frequency of incident radiation below its threshold frequency then no photoelectric effect takes place.

4. The maximum kinetic energy of photo electron is directly proportional to the frequency of incident radiation and independent of its intensity.

Please refer to the link below for CBSE Class 12 Physics Notes - Dual Nature of Matter and Radiation