the absorptive filter,
the interference or dichroic filters.
Optical filters selectively transmits light having certain properties (often, a particular range of wavelengths, that is, range of colours of light), while blocking the remainder.In astronomy, optical filters can be used to eliminate light from the Sun or from a star much brighter than the target object[1].
In our project we use filters in order to select the radiation with particular wavelength that is used by solar cell from the available spectrum of light source which is equal to that of sun's spectrum.
A monochromator is an optical device that transmits a mechanically selectable narrow band of wavelengths of light or other radiation chosen from a wider range of wavelengths available at the input[2].
Selecting Wavelengths is to isolate a wavelength of choice—and get it out of the monochromator—is to adjust the position of “the rainbow” so that a desired wavelength passes through the slit and the undesired wavelengths hit the edges of the slit and the inside wall of the monochromator around the slit and are blocked. This
is the reason why many monochromators are painted black inside so that light that strikes the walls of the monochromator is absorbed instead of reflecting around inside and possibly escaping through the exit slit. This fine adjustment, of which wavelengths fall where in the exit plane, is accomplished by slightly—very slightly—adjusting the position of the grating. In modern instruments, this is controlled by a servomotor controlled by a computer. The monochromator can be calibrated by
using a lamp with a well defined spectral line and adjusting the grating position until that line comes out of the exit slit. The grating’s position is then set to “display” that known wavelength. In some instruments this is done
automatically[3].
references:
1.http://en.wikipedia.org/wiki/Filter_(optics)
2.http://en.wikipedia.org/wiki/Monochromator
3.http://www.shsu.edu/~chm_tgc/primers/pdf/mono.pdf
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