Register to reply

Help w/ physics gre problem: radiation spectra

by yxgao
Tags: physics, radiation, spectra, w or
Share this thread:
yxgao
#1
Dec18-04, 03:05 AM
P: 124
64. Electromagnetic radiation provides a means to probe aspects of the physical universe. Which of the following statements regarding radiation spectra is NOT correct?

a. lines in the infaret, visible, and ultraviolet regions of the spectrum reveal primarily the nuclear structure of the sample.
b. the wavelengths identified in an absorption spectrum of an element are among those in its emission spectrum.
c. absorption spectra can be used to determine which elements are present in distant stars.
d. spectral analysis can be used to identify the composition of galactic dust.
e. band spectra are due to molecules.

The answer is a. This makes sense to me, but I'm not sure exactly why it must be the correct answer, and the others answers are false. Can someone explain each one in some detail?

Thanks!!
Phys.Org News Partner Science news on Phys.org
Scientists develop 'electronic nose' for rapid detection of C. diff infection
Why plants in the office make us more productive
Tesla Motors dealing as states play factory poker
Nylex
#2
Dec18-04, 04:18 AM
P: 551
Quote Quote by yxgao
This makes sense to me, but I'm not sure exactly why it must be right, and the others are false.
According to the question, if a is the answer then it must be false and the others are true.
dextercioby
#3
Dec18-04, 06:53 AM
Sci Advisor
HW Helper
P: 11,927
Quote Quote by Nylex
According to the question, if a is the answer then it must be false and the others are true.
Yes,Nylex is right,answer a) is the false one.According to the shell model of the nucleus,nucleons are disposed in enery levels,similar to electrons in the entire atom,but the main difference is that the gaps between successive energy levels is huge,in the order of MeV,so that should take the emission/absorbtion spectrum to the lower (wavelength) X rays and definitely gamma.

Daniel.

PS.And beside,all of the other answers are true...

Astronuc
#4
Dec18-04, 06:57 AM
Admin
Astronuc's Avatar
P: 21,880
Help w/ physics gre problem: radiation spectra

The key to why answer 'a' is wrong is found in " infared, visible, and ultraviolet regions of the spectrum" and "nuclear structure ".

The electromagnetic spectrum in this range is due to emission from 'atoms', or more specifically the change of state of 'electrons', which orbit the nucleus. They tell nothing of the nuclear structure.

b. is true - An atom will absorb light that is characteristic of its emission spectrum.

c. is true - since b is true.

d. is true - follows from 'c' and 'b'.

e. is true - band spectra
The combination of many different spectral lines resulting from vibrational, rotational and electronic transitions. Unresolved band spectra may appear as a spectral continuum. (from IIUPAC Compendium of Chemical Terminology)
yxgao
#5
Dec18-04, 02:50 PM
P: 124
Thanks a lot guys! I suppose that this was a rather simple question, looking back on it.


Register to reply

Related Discussions
Radiation physics, need help Introductory Physics Homework 2
Radiation Physics High Energy, Nuclear, Particle Physics 3
Questions on Line Spectra, Orbitals and Radiation Quantum Physics 4
Spectra of small molecule and computed spectra Biology, Chemistry & Other Homework 2
How Maxwell's theory of radiation could not explain atomic spectra? Quantum Physics 19