Questions tagged [electromagnetic-spectrum]

Questions about a certain range of frequencies of electromagnetic radiation, given e.g. as wavelengths or wavenumbers. Consider using the tag "wavelength" as well.

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4
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2answers
102 views

If my eyes were really big, would I see radio waves?

Considering an assertion that the fundamental difference between different ‘types’ of electromagnetic waves is frequency/wavelength, and larger antennas are needed for longer wavelengths, if my eyes ...
26
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3answers
4k views

Why do some electromagnetic waves continue travelling while others disappear?

Cosmic background radiation emitted when the Universe was very young still exists. But my wifi signal seems to disappear a short distance from my apartment. Why?
3
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0answers
28 views

What are the typical emissions of Jupiter's Aurorae?

I'm looking for some solid measurements of the full range of emissions from the Aurorae on Jupiter. I've found partial sets of data in the past which are most easily summarized here. As you can see, ...
12
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2answers
2k views

Why isn't most hydrogen in the universe molecular (diatomic), instead of atomic (monoatomic)?

Similar questions have been asked before; but, why? Is the monoatomic hydrogen left over from the Big Bang? And hasn't had the opportunity to collide with other hydrogen atoms yet? Or are hydrogen ...
3
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3answers
181 views

Spectrum of stars

If some specific metal is shown in a star's spectrum, does it indicate that the star has that specific metal? For example, the Sun, a G2 star, shows medium strength of Ionised Calcium in its spectrum, ...
0
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2answers
193 views

Does a photon need to have EXACTLY the right energy to be absorbed by a gas molecule?

From an answer to this question, https://physics.stackexchange.com/questions/281660/how-does-an-electron-absorb-or-emit-light, Absorption of a photon will occur only when the quantum energy of the ...
6
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2answers
129 views

Why is blue light extincted more strongly than red?

We know that blue light suffers extinction more strongly than red (examples include ISM, atmosphere etc.), but why? Is it a property of the shorter wavelength itself? Can someone provide a conceptual ...
-1
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1answer
65 views

If the Earth circled a red dwarf/giant or a brown dwarf, would its sky still look blue? [duplicate]

I have the impression that in brown dwarf and weak red dwarf systems, everything looks more reddish on a planet, including its atmosphere regardless of composition. Suppose there's a planet having an ...
1
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1answer
40 views

Missing line in solar spectrum

Referring to this answer to What's the rationale behind the false colours in solar observation photographs? which includes the table from Wikipedia's Fraunhofer lines: In the Table of wavelengths ...
1
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1answer
60 views

How to calculate the redshift of a line in a bunch of line spectra?

If in a spectra, there are many lines, mixed with gravitational redshift and non-redshift lines. For example, in this paper, they identify lines both redshifted and no-redshifted. Then how can i ...
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1answer
50 views

Do free protons and neutrons absorb much radiation? To affect astronomers' observations? If so, at what wavelength(s)?

In a plasma, or wherever, do the completely ionized nuclei commonly absorb much EM radiation? Or any free neutrons or protons? Can astronomers detect this? Enough so that astronomers take it into ...
5
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1answer
279 views

Would a red dwarf star resemble our own Sun at sunset to an observer on a nearby planet?

Suppose you're observing a red dwarf star at Noon from the surface of an Earth-like planet orbiting in the red dwarf's habitable zone, so that the red dwarf's luminosity is equal to our own Sun. Aside ...
8
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1answer
1k views

Why is Ganymede's aurora only visible in ultraviolet while Earth's is bright green and red?

GANYMEDE AURORAE NASA's Hubble Space Telescope observed a pair of auroral belts encircling the Jovian moon Ganymede. The belts were observed in ultraviolet light by the Space Telescope Imaging ...