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An example of this phenomenon is when clean air scatters blue light more than red light, and so the midday sky appears blue (apart from the area around the Sun which appears white because the light is not scattered as much). The optical window is also referred to as the "visible window" because it overlaps the human visible response spectrum.
This method involves coating LEDs of one color (mostly blue LEDs made of InGaN) with phosphors of different colors to form white light; the resultant LEDs are called phosphor-based or phosphor-converted white LEDs (pcLEDs). [34] A fraction of the blue light undergoes the Stokes shift, which transforms it from shorter wavelengths to longer.
The condenser lens acts to project this light, without focusing it, through the sample. This illumination scheme creates two sets of conjugate image planes, one with the light source and its images and one with the specimen and its images. These two sets of image planes are found at the following points (see image for numbers and letters):
One example of the photo-excitation scheme is a method developed by Michael Bowers, at Vanderbilt University in Nashville, involving coating a blue LED with quantum dots that glow white in response to the blue light from the LED. This method emits a warm, yellowish-white light similar to that made by incandescent light bulbs. [32]
It is called the white point of the image. The process of calculating the white point discards a great deal of information about the profile of the illuminant, and so although it is true that for every illuminant the exact white point can be calculated, it is not the case that knowing the white point of an image alone tells you a great deal ...
The majority of black-and-white infrared art, landscape, and wedding photography is done using orange (Wratten #15 or 21), red (#23, 25, or 29) or visually opaque (#72) [d] filters over the lens to block the blue visible light from the exposure. Very dark-red (#29) filters block out almost all blue, and visually opaque (#70, 89b, 87c, 72 ...
Figure 1: Schematic layout of a White-light Interferometer. A CCD image sensor like those used for digital photography is placed at the point where the two images are superimposed. A broadband “white light” source is used to illuminate the test and reference surfaces. A condenser lens collimates the light from the broadband light source.
Spectrum of a blue/green electroluminescent light source for a clock radio (similar to the one seen in the above image). Peak wavelength is at 492 nm and the FWHM spectral bandwidth is quite wide at about 85 nm. Electroluminescence is the result of radiative recombination of electrons and holes in a material, usually a semiconductor.