1. Gustav Kirchoff, Robert Bunsen

2. Kirchoff’s Rules of Spectroscopy
A hot solid or liquid body produces a rainbow or continuous
spectrum.
A hot but low-density gas emits a spectrum of lines that is
characteristic of the gas. This emission spectrum or
bright-line spectrum can be used to identify the gas,
since it’s unique, like a fingerprint.
If a continuous spectrum or rainbow of colors passes through
a cooler low-density gas, the gas will absorb the very same
colors that it would have emitted if it were hot.
This absorption spectrum appears as a series of dark lines
on top of a rainbow.
The spectrum of a star is an absorption or dark line spectrum.

3. This is the spectrum of
the sun.
It is a dark-line or
absorption spectrum.