AND MATTER - - - - Unit dual nature of radiation and matter The minimum energy needed for an electron to escape from the metal surface is called work function of that metal . The work function of the metal is denoted by φ and is measured in electron volt (eV). The SI unit of energy is joule. But electron volt is a commonly used unit of energy in atomic and nuclear physics.
One electron volt is defined as the kinetic energy gained by an electron when accelerated by a potential difference of V. eV = KE gained by the electron = Work done by the electric field = q V = . × – C × V = . × – J Note Suppose the maximum kinetic energy of the free electron inside the metal is .
eV and the energy needed to overcome the surface barrier of a metal is eV, then the minimum energy needed for electron emission from the metallic surface is – . = . eV. Here .
eV is the work function of the metal. The work function is different for different metals and is a typical property of metals and the nature of their surface. Table . gives the approximate value of work function for various metals.
The material with smaller work function is more effective in electron emission because extra energy required to release the free electrons from the metal surface is smaller. charge. However, later experiments showed that under certain circumstances, they exhibit wave-like properties also. In this unit, the particle nature of waves (radiation) and the wave nature of particles (matter) – that is, wave-particle duality of radiation and matter is discussed with the relevant experimental observations supporting this dual nature.
. . Electron emission In metals, the electrons in the outer most shells are loosely bound to the nucleus. Even at room temperature, there are a large number of free electrons which are moving inside the metal in a random manner.
Though they move freely