# Tag Info

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For many materials the change in refractive index over the range of visible wavelengths isn't huge, so it's not a bad approximation to take a single value. The range of visible wavelengths is from about 400nm to 700nm, so the middle wavelength is 550nm. As it happens, the sodium D lines are not far from this, at 589nm, and since they are bright and easy to ...

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Using the basic equipment at your disposal, this will not be possible. A naive approach would be to take the measured line amplitudes, divide by the line-integrated absorption coefficients at the wavelength of each line for some nominal set of parameters characteristic of the solar atmosphere, then divide out the emission coefficients and compare the ...

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What emission lines? Unless you are looking at the chromosphere or corona the Sun does not have emission lines. Of course you can estimate photospheric abundances from a photospheric absorption line spectrum. That is how the solar abundances are estimated for most elements. However, you need a good spectrum to perform a detailed analysis. It should have ...

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I think it might be one of those things where people do something because everybody does. I agree with you, a figure of merit that includes noise would make more sense. But, as the circuit designer that I am, I could also say that that wouldn't be the end of it. For example, in the classic trans-impedance amplifier used for these kind of detectors the ...

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One half of the problem is light. Light is an oscillating electromagnetic field. The frequency of oscillation determines the color. Higher frequencies have shorter wavelengths and are blue. Lower frequencies have longer wavelengths are red. Light is a mix of a range of wavelengths. Sunlight contains a wide range of wavelengths, including some that are too ...

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I believe the point Mew is trying to make is that 'red' is a range of wavelength. Although your laser has a very narrow range of red wavelength, I suspect the range of wavelength reflection in the green pigment of the ball is much broader and may even have a range of red in it. An interesting, although perhaps unrealizable experiment would be to find a ...

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When we say a red ball absorbs other colors, it doesn't mean it absorbs them perfectly. It can reflect non-red light, just less strongly than it reflects red. Beyond that, color vision is extremely complex. Your brain does amazing things trying to compensate for the color of light in a scene.

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Parallel rays reflecting on a concave mirror do intersect at one point, the focus, if the mirror is a parabola (in 2d plane geometry) or paraboloid (in 3d space geometry).

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Both operations are equivalent, up to a local phase in the second mode. In particular, if you shift the second basis vector's phase by $i$, then you will turn $H$ into $A$. In a beam splitter this is perfectly natural, because the phases of the output modes are not particularly well defined, and you can always model the difference between the two operations ...

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There are photons traveling in all directions, not just the dozen or so you show. The further from the source the telescope is, the smaller the amount of solid angle it covers and the fewer photons it will gather. A $1 m^2$ telescope pointed at the sun will receive about $1.4 kW$. Taking a typical photon energy of $2 eV$ that is about $4.2E21$ ...

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This question is too broad. It involves ALL the objects in the universe which have a surface, i.e., everything. I'm going to avoid giving a lecture here. In some liquids and most gases the electronic structure of each individual atom or molecule is enough to describe their spectra. The "property" you are looking for in the case of solids is the band ...

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