Explain emission lines and absorption lines.

(N/A) $1$. Emission Lines: When an atom in an excited state transitions to a lower energy state,it emits a photon with energy equal to the difference between the two energy levels $(E_2 - E_1 = h
u)$. This results in a bright line in the spectrum at a specific wavelength,known as an emission line.
$2$. Absorption Lines: When an atom in a lower energy state absorbs a photon of energy exactly equal to the difference between its current state and a higher energy state $(h
u = E_2 - E_1)$,it transitions to the higher state. This removal of specific wavelengths from a continuous spectrum creates dark lines,known as absorption lines.