Question

how does the spectrum of a star help in determining its composition?

Answer 1

It's a long topic, watch this https://www.youtube.com/watch?v=GhAn8xZQ-d8

then ask if you still have questions

Answer 2

suppose the energy difference between two levels is 10 ev and a photon of energy 11 ev is incident on the atom, am I right if I say that 10 ev is used up in transition btwn levels and only 1ev light comes out the other side?

Answer 3

No, photons are quantized and you can't split them apart. It is either absorbed or not.

Answer 4

oh.. ok i read that as we heat a material (say iron) it changes colour depending on temperature , so how do astrophysicists determine the composition, i mean if sodium emits an yellow flame at a particular temperature doesn't it shift to higher frequencies of radiation when heated to higher temp ,then it no longer emits its characteristic yellow flame??..im confused...

Answer 5

not quite, the transitions are fixed, regardless of the temperature the characteristic photons at those wavelengths are emitted. If you raise the temperature, you may see more lines because of access of electrons to higher energy states.

The relaxation events are when the photons are emitted, typically, if the electron has energy between two transitions it will relax (through vibrations) to the nearest lower energy state and relax from there (to a lower energy state).

What you talked about in the beginning (heating iron) is different, that is called black body radiation.

Answer 6

or to rephrase the above question how and why is emission spectrum produced instead of a continuous spectrum when say an element is heated?

Answer 7

That is a really good question, but to be honest i dont know, I'll look it into it but i can't promise anything. You should repost

" how and why is emission spectrum produced instead of a continuous spectrum when say an element is heated?"

as a new question. I'm sure someone that knows will see it if I dont find the answer first.

Answer 8

ok ..thanks :)

Answer 9

no prob !