Which of the following os not characteristic of the cosmic background radiation?

Question

a) it is perfectly thermal b) it peaks in the microwave regime c) it is isotropic d) it is due to the synchrotron process

Answer 1

Hi Nichole

I suspect this is a homework question, so I won't answer it for you, but will help you work towards an answer. The answer options are exploring your knowledge of the CMBR and the reasons why we think it is left over from the big bang.

(a) it is perfectly thermal
A perfectly thermal radiation distribution conforms to a Planck blackbody distribution. This option asks whether or not the CMBR has a (close to) perfect blackbody frequency distribution. If it *does*, then it is unlikely to have come from any source other than the big bang.

(b) it peaks in the microwave regime
The frequency distribution of the CMBR has a peak, and if the distribution is thermal then this peak allows us to assign a temperature to the distribution. This option is obviously true, because it's called the "cosmic microwave background radiation". :o)

(c) it is isotropic
"Isotropic" means it is the same in every direction. If the radiation distribution looks the same in every direction then it can not have a point source outside the earth (because the point source would leave preferred directions in the distribution). If the CMBR is isotropic then it must have come from "everywhere" (as in the big bang model) rather than from a single late source.

(d) it is due to the synchrotron process
Synchrotron radiation is produced by accelerating charged particles through magnetic fields. Synchrotron radiation is produced at frequencies (and energies) characteristic of the speed of the charged particles, so it is not a thermal distribution. It is also source specific, so it doesn't produce isotropic radiation baths.

That should be enough hints for you to get the answer. :o)


Hope this helps!
The Chicken

Answer 2

Think about them:
B and C are clearly characteristics of the CMB. It is radiation that is predominantly in the microwave regime and since it is in the "background" it indicates isotropy, it comes from everywhere. If it came from a localized source, it wouldn't be in the "background."

Now the other two (A and D) contradict each other. Thermal radiation is produced by a hot opaque source, while synchrotron radiation Synchrotron radiation is the radiation which is produced when charged particles are accelerated in a curved path or orbit, you get your radiation from one source or the other.

Check out your information on the CMB and find out which of these two processes are responsible for producing the radiation and you will have you answer.

Answer 3

i dont know... but i know its there due to planets moving away from each other and supposedly the remenants of a massive explasion that created the universe!! thast all i know on the matter.. u'll be lucky to get someone smart on this that will bother to answer sensibly! i would guess a...