Question

Which nature of light is supported by the phenomenon of photoelectric effect? Write Einstein's equation related to photoelectric emission and briefly explain the laws of photoelectric emission on its basis.

Hint:

The photoelectric effect demonstrated the particle nature of light, where photons transfer energy to electrons, leading to their emission from a metal surface.

Answer 1

The phenomenon of the photoelectric effect supports the particle nature of light. When light of sufficient frequency (threshold frequency) is incident on a metal surface, electrons are emitted from the surface. This phenomenon could not be explained by the wave theory of light, but Einstein's quantum theory of light provided a clear explanation. According to this theory, light consists of discrete packets of energy called photons. When a photon strikes the metal surface, it imparts its energy to the electron, causing the electron to be ejected from the surface.
The Einstein equation for photoelectric emission is given by: \[ E_{\text{photon}} = h\nu = \phi + K.E. \] Where: - \( E_{\text{photon}} = h\nu \) is the energy of the incoming photon,
- \( h \) is Planck's constant,
- \( \nu \) is the frequency of the incident light,
- \( \phi \) is the work function of the metal,
- \( K.E. \) is the kinetic energy of the emitted electron.
Laws of Photoelectric Emission:
1. Emission of Electrons: When light of frequency greater than or equal to the threshold frequency strikes a metal surface, electrons are emitted.
2. Effect of Intensity: The intensity of light affects the number of electrons emitted, not their energy. Higher intensity leads to more emitted electrons.
3. Effect of Frequency: The energy of emitted electrons depends on the frequency of the incident light. Electrons are emitted only if the frequency of light is above the threshold frequency, regardless of intensity.