Question

Tell me some applications of photoelectric cell ??

Answer 1

Application of Photoelectric Cell

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1. It plays an important role in a television studio. It converts
light and shade of the picture into electrical waves which, after a proper processing, are transmitted to distant stations.
2. It is used for reproduction of sound in films. Microphone converts sound into electrical waves which, after amplifications, are fed to an electric lamp. Intensity of light from this lamp records lines of varying transparency on the film. During reproducing, a beam of light falls on a photocell, after crossing through this film. Photocell converts light back into electrical oscillation which produces sound when fed to the receiver.
3. It is used for triggering fire alarm. In factories using chemicals or explosive materials, photocells are fitted at selected places. Light from any accidental fire falls on the cell. This produces a current which, after amplification, is fed to an alarm.
4. It is used in operating burglar's alarm. Ultraviolet light from a source is incident constantly on a cell. Any unwanted person entering a room cuts that beam unknowingly, thus stopping the current for a fraction of a second. This triggers an alarm.
5. It is used for automatic switching of street light. Light from sun, during day, falls constantly on the cell making a current to flow through the circuit continuously. This current after amplification is fed to an electromagnet which keeps the key of the street light circuit open. In the evening, after sunset, intensity of light and hence the current decreases. The electromagnet loses its strength. As a result of this, the key is closed and the street light is automatically switched on.
6. A photocell coupled with an electronic counter can be used to count, automatically, the number of persons entering or leaving a hall. Each person will cut a beam of ultraviolet light once, thus producing a kick in the counter.
7. It is used to compare the illuminating powers of two sources. Current produced is directly proportional to intensity, which, in turn, is proportional to the illuminating power of the source. Ratio of deflection in ammeter with two sources of light gives the ratio of their ill
powerS.