GREPhysics.NET: GR0177 #64

GR0177 #64

Problem

GREPhysics.NET Official Solution

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Atomic $\Rightarrow$ }Radiation Spectra

Choice-by-choice analysis gives...

(A) The word nuclear sounds questionable, as lines are often due to just spin-splitting.

(B) The wavelengths of absorption spectra are often close to that of emissions spectrum (or overlapping). This is true.

(C) Absorption spectra is often used in astrophysics to determine the contents of stars. Even though mere mostly harmless Earthlings have never visited the sun, the absorption spectra of the sun helps determine its component elements.

(D) Same idea as in the previous choice.

(E) A single atom does not have band spectra. So, yes, band-spectra are due to molecules. (To wit: it only has, say, 2s, 3p, etc., states, and not states that are split in-between---molecules have more degrees of freedom, i.e., they can rotate and vibrate, while atoms can't.)

The remaining choice is (A). Take that.

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Comments

aziza
2013-09-26 17:06:35

I interpreted "nuclear structure of the sample" by taking "sample" to mean a galaxy or watnot, and its nuclear structure to be the core structure, which in AGN's (black holes etc) we mostly do probe with UV spectra...

yummyhat
2017-10-26 20:15:50

feelsbadman

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Lilith
2010-11-12 01:00:19

Haha, love the reference to the Hitchhiker's Guide in Yosun's answer!

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wikiwert
2010-10-05 15:17:04

I would like to add that the absorption spectrum is contained in the emission spectrum, because the absorption spectrum typically includes transitions fom the ground state (or a low energy state) to a higher one; that is, n=1 to n>1.
But the emisson spectrum includes transitions from n to m with mReply to this comment

Atrain
2010-10-01 23:34:05

If you're not as smart as Yosun:

A) infra-UV seems a bit low-energy for nuclear transitions
B) energy levels are the same distance apart whether the electron jumps up or down
C) well, it works here on Earth, so why not
D) fancy restatement of C
E) huh? well, molecules have multiple atoms, and a "band" sounds like something you'd get by putting multiple "lines" together, so this I guess is reasonable

which leaves A.

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ramparts
2009-10-08 12:35:36

Woohoo! Throwaway question for the astro majors! We don't get many of those on this test.

gremonkey
2011-11-11 17:09:06

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ramparts
2009-10-08 12:35:35

Woohoo! Throwaway question for the astro majors! We don't get many of those on this test.

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sharpstones
2007-04-09 19:17:40

I think it would be easier to just remember that nuclear energy levels transitions result in the emission of a gamma ray. Like the transitions of an electron in an atom only electron transitions emit X-rays.

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If you're not as smart as Yosun: A) infra-UV seems a bit low-energy for nuclear transitions B) energy levels are the same distance apart whether the electron jumps up or down C) well, it works here on Earth, so why not D) fancy restatement of C E) huh? well, molecules have multiple atoms, and a "band" sounds like something you'd get by putting multiple "lines" together, so this I guess is reasonable which leaves A.

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