Explain the working of a photo emissive cell. Write any two applications of photo electrics cells.

A photoemissive cell, also known as a photoelectric cell, is a device that converts light energy into electrical energy based on the principle of the photoelectric effect. The photoelectric effect refers to the emission of electrons from a material when exposed to light of sufficient energy. Photoemissive cells are typically composed of a photosensitive material, such as a metal, which emits electrons when photons (light particles) strike its surface.

Here's a step-by-step explanation of the working of a photoemissive cell:

Incident Light: When light falls on the surface of the photoemissive material, the photons carry energy. The photons transfer their energy to electrons within the material.

Absorption of Photons: The photons are absorbed by the atoms in the material, causing the electrons within the atoms to gain energy.

Emission of Electrons: If the energy of the absorbed photons is sufficiently high, it can overcome the binding forces holding the electrons within the atoms. This leads to the emission of electrons from the surface of the material, resulting in a flow of electric current.

Electron Collection: The emitted electrons are collected by a positively charged electrode placed in close proximity to the photosensitive material. The electric potential difference between the material and the electrode causes the electrons to be attracted and move towards the electrode.

Current Generation: The flow of electrons towards the electrode constitutes an electric current, which can be measured and utilized for various applications.

Applications of photoelectric cells include:

Photocells in Light Sensors: Photoelectric cells are widely used in light-sensing applications, such as automatic lighting control systems. They can detect changes in ambient light levels and trigger the activation or deactivation of lighting fixtures accordingly. For example, in streetlights, photoelectric cells can sense the decreasing light levels at sunset and automatically turn on the lights.

Solar Cells: Solar cells, or photovoltaic cells, are a type of photoelectric cell that convert sunlight directly into electricity. They are used extensively in solar panels to generate clean and renewable energy. Solar cells are employed in a variety of applications, ranging from residential and commercial power generation to spacecraft and satellites, where they provide an efficient means of harnessing solar energy.

These are just a few examples of the numerous applications of photoelectric cells, which have found widespread use in various fields including electronics, energy, and sensing.