Applications

(i) Photo-emissive cells:

(a) These are used in photometric applications.
(b) Used as a photo multiplier for large output.
(c) Used in photographic equipments.
Some of the important uses of photo cells are as follows :
1. Vacuum type photoemissive cells are used in photometry for measurement of light intensity.
2. Gas filled type photoemissive cells are used in the reproduction of sound in cinema films.
3. Photovoltaic cells are used in converting solar radiation into electrical energy as solar batteries.
4. Photocells are used to switch on and switch off the street lights automatically.
5. Photocells together with switching circuits are used for automatic opening and closing of doors.
6. Photocells together with relay circuits are used to control the temperature of a furnace.
7. They are used in automatic fire alarms and automatic burglar alarms.
8. They are used to control the thickness of paper in paper industry.
9. Photocells are used in astronomy to estimate the temperatures of stars.
10. They are used in cosmetic industry as complexion meters.