What Is Photometer ?Photometer is a device which is used to measure the strength of electromagnetic radiation in the range from ultraviolet to infrared and including the visible spectrum. Such devices are generally transducers that convert an electric current into a mechanical indication—e.g., a pointer moving across a dial. The source of the current may be a selenium cell, which generates a current when light falls on it, or it may be a permanent source, such as a battery, in which case the current passes through a cadmium sulfide cell whose resistance varies with the amount of light falling on it.
Principal Of Photometer :-Most photometers detect the light with photoresistors, photodiodes or photomultipliers. To analyze the light, the photometer may measure the light after it has passed through a filter or through a monochromator for determination at defined wavelengths or for analysis of the spectral distribution of the light.
Working Of Photometer :-The system includes a non-moving, truncated paraboloid of revolution, having a paraboloid axis, a small entrance aperture, a larger exit aperture and a light-reflecting inner surface that receives and reflects light in a direction substantially parallel to the paraboloid axis. A system of wide field of view lenses can be substituted for this optical arrangement depending on the application. The system also includes a light processing filter to receive and process the redirected light, and to issue the processed, redirected light as processed light, and an array of light receiving elements, at least one of which receives and measures an associated intensity of a portion of the processed light. The system tracks a light source moving along a path and produces a corresponding curvilinear image of the light source path on the array of light receiving elements. Undesired light wavelengths from the light source may be removed by coating a selected surface with a coating that absorbs incident light in the undesired wavelength range .
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