Question

Define the photoelectric effect. Write the laws of the photoelectric effect.

Answer 1

Photoelectric effect is discovered by Albert Einstein and received Nobel Prize for this invention. Photoelectric effect is defined as when it absorbs electromagnetic radiation electrically charged particles are released from or within a material. Electrons emitted during this process are called photoelectrons. The effect results when light falls on electrons from a metal plate. Infrared, visible, ultraviolet light, X-rays, gamma rays are the radiant energy. It is important in Development of modern physics.

Complete step by step answer:
The effect is based on electromagnetic radiation. Photons are made of a series of particles. On a metal surface When a photon hits an electron, and emits an electron. Emitted electrons are called photoelectrons. This effect is also called Hertz Effect. Minimum frequency which is needed is called "threshold frequency'.
The energy of a photon is find out by $E = hf = KE + w$
Where $h$ is Planck’s constant, f is the frequency, KE is the energy of photoelectron, w is the work function

Laws of Photoelectric effect:
• There is a definite cut off frequency in which electrons cannot be ejected.
• Intensity of light incident is directly proportional to the number of electrons emitted.
• Kinetic energy of electrons which is emitted depends on the frequency of incident light on any substance.
• No time logging between the emission of electrons and incident of light.

Hence, the correct answer is option (B).

Note: To detect light, Photoelectric cells are used.
• Solar cells and fiber optics telecommunications uses phototubes.
• Many metal plates called dynodes are in photo multipliers.
• It is used to understand the quantum nature of light and electron energy levels in matter.
• This effect is widely used in imaging technology.
• Photocopies, light meter, photodiodes, phototransistors have the applications of Photoelectric effect.