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A quick look at the Del Sol How it Works page shows their explanation, HOW DOES IT WORK? The Spectrachrome® crystal reveals color upon irradiation by ultraviolet waves; i.e., sunlight. When a flower blooms, the result is the exposure of the inherent color of the flower. A Spectrachrome® crystal is similar in that an energy-shift occurs causing the ...


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There is an explanation on the Del Sol web site but it omits the technical details. This is probably because Del Sol regard it as commercially valuable confidential intellectual property, and I have to concede that they are probably correct. Anyhow, some Googling has turned up a suggestion for how it works but there is no proof for this idea so treat it as ...


4

I believe the dyes behave similar to glow in the dark materials; They fluoresce a certain wavelength over time after being radiated. In the case of these shirts you'll have different chemicals for different colours, but which are all "activated" by UV radiation. There is a pretty nice explanation on Wikipedia, but basically this: You can excite an ...


4

To discriminate between the other two answers. Lifetime spectroscopy would be capable of distinguishing between photochromism (in this case, reversible ultraviolet-switchable reflectance, example: hexaarylbiimidazole where the transition time is milliseconds to seconds) and ultraviolet fluorescence (where the "transition time" is zero, although the excited ...


3

(the following answer is included essentially in "The Feynman LECTURES ON PHYSICS-Mechanics, Radiation & Heat ,Vol. 1, 26-3 Fermat's principle of least time.) Suppose you are at point A in the land and a screaming girl is at point B in the sea. You can run with a speed $\:v_{1}\:$ on the land greater than the speed $\:v_{2}\:$ you can swim in the ...


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In Wikipedia the caustic is defined as follows. In optics, a caustic is the envelope of light rays reflected or refracted by a curved surface or object, or the projection of that envelope of rays on another surface. You can think of the envelope of a family of curves as a curve that is a tangent to each of them. Here is a diagram on page 60 of "A Treatise ...


2

It is not clear to me what you meant by " I measured the size of the image on the surface of the lens". You calculated value of approximately 2 was done on the assumption that the object was in the focal plane of the convex lens of focal length $f = 12$ cm. If the height of the size is $h$ the best the naked eye can do is to view the object at the least ...


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Coherent sources- Two sources of light are said to be coherent if the waves emitted from them have the same frequency and are 'phase-linked'; that is, they have a zero or constant phase difference. The calculation yielded 90.pi ; We know that 2.pi denotes a phase change of zero as the waves will come back to initial phase relation of the coherent ...


1

Comparison of fabrication techniques for hollow retroreflectors describes, in great detail, the two obvious methods: The use of a precision solid prism corner cube as a mandrel to hold the glass plates prior to gluing of the edges. An adjustable set of precision mirror mounts, designed to hold the three plates In both cases interferometric techniques ...


1

If you just have collimated light going into the system and nothing at the image plane then, yes, there will be nothing but collimated light coming out of the last lens and you could put the image screen where ever you want (and not see an image anywhere). But, if there is something at the "input" plane it scatters the incoming collimated light and its ...



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