Wha Is Photocell?
Electromagnetic energy or light is the source of wide range of sensors also known as photocells. These photocells are the most important part of new technologies, which are created worldwide. Many different forms of photocells are available in market, like solar panels (use to convert solar energy i.e. light into electricity) or photoresistors (used to vary resistance with light).
Photoresistors are the most commonly used photocell. A semiconductor having high resistance is used to construct devices like photoresistor. The semiconductor absorbs the required number of photons, when light greater than the threshold value falls on the semiconductor. The absorbed photons, now energizes the electrons present in the semiconductor and enters in the conduction state (indicates decrease in resistance). A photoresistor made up of pure silicon without any impurities is known as intrinsic, for any variation in resistance, they have higher threshold values while a photoresistor having an impurity, mainly dopant, is known as extrinsic. These are highly sensitive as compared to intrinsic and have low threshold values.
All the devices that use light in any way make use of photoresistors. Such as, in some clock displays, photoresistors are used to make them more readable according to intensity of the light present. Photoresistors are used to turn on or off the lights according to their need; this can be very useful in case of street lights and nightlights that people use in their homes. Photoresistors are very useful for a photographer too; the modern cameras use this technology which helps in adjusting the aperture and shutter speed to have a best shoot.
Photovoltaic cell is another type of photocell, which is widely used. It is also called solar cell. In this, the electromagnetic radiations are used to release the electrons to produce electric effect or electricity, this is a photovoltaic effect. With the help of this effect the electricity can be produced from the renewable source of energy and it can be temporally stored in a battery system.
Other specific types of energies are also focused by different types of photocell. Modern thermometers use optical detectors. In these thermometers, the increase in ambient temperature is exactly determined by the increase in energy due to electromagnetic radiations or the surface measures on which the light is falling. Cryogenic detectors are also a type of photocell, a single bit of electromagnetic radiations (such as x-ray or infra-red photon) can be easily detected with the help of this detector. It is a very sensitive device.
Chemical photocell is one of most basic type of a photocell. Photographic plate in a non-digital camera is made up of this type of photocell. Now to create the image on the photographic plate, it is exposed to light and silver halide molecules break up into two atoms (halogen atom and metallic silver atom). But the modern cameras use another type of photocell known as charge coupled devices instead of chemical photocell. These devices work by transferring electric charge.
Category: Technology