Question

Concept Application The sun is primarily comprised of hydrogen, but it emits white light due to the closeness of atoms in the sun. In the early 1800s Joseph von Fraunhofer observed that several parts of the spectrum were missing from the sun, and one of these missing parts was measured at a wavelength 656.3 nm. Why is this line missing from the solar spectrum, despite being made of mostly hydrogen?

Answer 1

The wavelength corresponding to 656.3 nm corresponds to first absorption line of Balmer Series. This corresponds to electron jumping from n=2 to n=3 by absorbing the photon. Because the electrons in the Hydrogen atoms of the Sun absorbs at around 656.3 nm, this line is missing from the absorption spectrum.

Further explanation

For Balmer series of Hydrogen spectra, we have,

$\frac{1}{\lambda}=R_H\left (\frac{1}{n_i^2}-\frac{1}{n_f^2} \right )\\ \Rightarrow \frac{1}{\lambda} =10973731m^{-1}\left(\frac{1}{2^2}-\frac{1}{3^2} \right )\\ \Rightarrow \frac{1}{\lambda}=1.524\times 10^{-6}m^{-1}\\ \Rightarrow \lambda\approx 656 nm$