Question

a) Given that the Sun’s photosphere is at a temperature of ~6000 K, would you expect collisional or radiative excitations to be more important in exciting hydrogen atoms to the second (n=2) level?

            (b) Would you expect the Lyman a (n = 1 -> 2 or 2 ->1) line to appear in emission or absorption? Justify your answer.   

Answer 1

(a) in sun's photosphere where the temperature is about 6000 Kelvin ,the radiative excitations are more important than collisional (having lower energy) in exciting the electrons of hydrogen atom to n = 2 level.

(B)

lyman alpha n(1-->2) Transitions require energy to be observed, thus a line would appear as absorption spectra .

the transition n(2-->1) emits energy in the form of radiation thus will be observed as the emission spectra .

emission and absorption spectra of a same atom are like negative and positive of each other that is complementary to each other.