Why are there fewer lines on the absorption spectrum than on the emission spectrum for some gases?

Question

I don't know if this is right, but I think that it is because:

• when the gas is heated, the electrons get 'excited' and move up to an energy level (lets say an electron moves up 4 energy levels).

• Then as they move down, they emit all 4 photons of different wavelengths which are then shown on the emission spectrum.

• when the star's light goes through the gas, the gas absorbs specific wavelengths which causes their electrons to get 'excited'. This time, if the electrons move up 4 energy levels with this one specific wavelength they have absorbed, then you can't see the 4 other wavelengths that were emitted? Thus, 4 lines are missing from the absorption spectrum?

I don't know if this is correct...

Thanks for any help.

Answer 1

I found the answer!

So the continuous spectrum is formed is usually formed from a heated body (i.e a heated filament or a star) and when the continuous spectrum passes through a cooler gas, the electrons in the gas absorb the energy of a photon with a specific wavelength (which is why is shows black lines against a continuous spectrum).

• The electrons then get excited and move up an energy level. As they move down, they emit photons with energy of the discrete energy levels of an atom.

In the emission spectrum, the electrons in the energy levels usually start at random energy levels and so there is more of a variety of wavelengths that could possibly be emitted.

Whereas in the absorption spectrum, there are a few lines missing because most electrons start from ground state, meaning that there are less options of energies that a photon can be emitted at.