 | rare light bulbs and lamps |
| glossary of terms |  |
What is PHOTOMETER?
A photometer is a device for measuring or comparing intensities of light.
Here is a basic photometer.
The standard candle or lamp #A, and the electric lamp #B under test, with the screen #C and scale #S between them are placed in a dark room so that one side of the screen may be illuminated by the candle alone and the other side by the lamp alone.
By moving the screen, a position can be found were both sides will be equally illuminated.
Suppose that such a position has been found and that distance d1 and d2 have been read from scale #S.
If B1 is the candlepower of #A, and B2 is the candlepower of #B, then formula as follows is true.
references for this page: PHOTOMETER, ELEMENTARY PHOTOMETER