Question

Why do hydrogen and mercury lamps produce different colors? Why is the emission spectrum from hydrogen interesting?

Answer 1

answer) hydrogen and mercury lamps produce different colors because in the lamp when the hydrogen and mercury are heated, the the electrons of both these molecules excite to higher energy shells, when they excite to higher energy states, they don't stay there for long and return back to its original excited state and when they return back to their original state or lower energy shell, they emit the extra energy in form of light energy , this light energy is related to different wavelength of light by the formula

E=hc/$\lambda$,

and each shell has different energy levels, like when an electron excites from shell 2 to shell 5, and returns back to shell 2, its has shell 5,4,3 and then 2, so each shell emits different amount of energy which has different wavelength and different wavelength of light corresponds to different colors, so this is the reason hydrogen and mercury bulbs have different colors.

emission spectrum of hydrogen is interesting in the sense that hydrogen contains only a single electron but it emits different colors when heated because the hydrogen atom a lot of different energy shells to which this electron can jump to and then return back to lower energy shell or state, when  it comes back from higher energy state to lower energy state, it emits light energy of various wavelength which corresponds to different colors due to these high number of shells, therefore the emission spectrum of hydrogen has multiple spectral lines.