Astrophysics - star color index

hfenton
Messages
5
Reaction score
0

Homework Statement



If a star emits the same intensity of radiation at all visible wavelengths, what will be its
apparent color at the Earth’s surface?

Homework Equations



No equations...

The Attempt at a Solution



I realize that a horizontal line would occur through the visible spectrum if a curve was plotted on an intensity/wavelength diagram, however, considering there is no true peak in the visible colors, I have no idea what color is likely to be seen. I have thought that it might be white or black, but am not really confident with those answers. any help would be appreciated.
 
Physics news on Phys.org
Because human eyes are sensitive only to the visible spectrum, so narrow it down :wink:
As you deduce, there are only 2 possible cases: white or black. When is a thing black to our eyes?
 
we see black when light is not present. therefore, would this star have to be pure white? Then, because I am seeing it from Earth's surface, should I take into account the effects our atmosphere has on light, such as scattering? I think I am making this problem more difficult than it is.
 
I also think you're making it more complicated than expected, but making problems complicated is crucial for reasoning :biggrin: Fortunately you're right in this case I think.
Have a look at this: http://en.wikipedia.org/wiki/Diffuse_sky_radiation. I suppose that we don't have to gaze at the Sun :biggrin: so the intensity of light from the star here is small (we know that stars except the Sun are not so bright when observing from the Earth), i.e. we have to look directly to it. Since the shorter wavelength radiation is easier to be scattered by the atmosphere, what we receive if looking directly to the star is more of longer wavelength radiation.
Anyway I'm no expert, so don't rely on my thought :biggrin: Justify it yourself :wink:
 
Thread 'Need help understanding this figure on energy levels'
This figure is from "Introduction to Quantum Mechanics" by Griffiths (3rd edition). It is available to download. It is from page 142. I am hoping the usual people on this site will give me a hand understanding what is going on in the figure. After the equation (4.50) it says "It is customary to introduce the principal quantum number, ##n##, which simply orders the allowed energies, starting with 1 for the ground state. (see the figure)" I still don't understand the figure :( Here is...
Thread 'Understanding how to "tack on" the time wiggle factor'
The last problem I posted on QM made it into advanced homework help, that is why I am putting it here. I am sorry for any hassle imposed on the moderators by myself. Part (a) is quite easy. We get $$\sigma_1 = 2\lambda, \mathbf{v}_1 = \begin{pmatrix} 0 \\ 0 \\ 1 \end{pmatrix} \sigma_2 = \lambda, \mathbf{v}_2 = \begin{pmatrix} 1/\sqrt{2} \\ 1/\sqrt{2} \\ 0 \end{pmatrix} \sigma_3 = -\lambda, \mathbf{v}_3 = \begin{pmatrix} 1/\sqrt{2} \\ -1/\sqrt{2} \\ 0 \end{pmatrix} $$ There are two ways...
Back
Top