1. Continuous, Emission, and Absorption
Three types of Spectra
Continuous, Emission, and Absorption

2. Continuous Spectra and Blackbodies
The intensity different wavelengths (or frequencies) of E-M radiation from a blackbody,
(or an object like a blackbody i.e. a solid or a high pressure gas like a star or gas giant)
changes gradually.
They emit a continuous spectrum
Intensity of specific wavelengths may vary but there are no gaps .

3. The Photo-Electric Effect
A Photon is created when an electron jumps from a higher to a lower energy orbit.
The wavelength of the photon depends on the Energy difference between the orbits.
So the unique orbit pattern of each element or compound
creates certain specific wavelengths of light.
It can also absorb only those wavelengths light.

4. Emission Spectra
A hot gas only gives off the specific wavelengths of light that match its molecules.
These spectra will appear as bright lines at specific wavelengths with gaps in between… an Emission Spectrum
The pattern of bright lines in the emission spectrum from a hot, glowing gas tells us what it is made of.

5. Absorption Spectra
When light is reflected off or passes through a cool gas it is absorbed, but only those wavelengths that the specific gas can absorb
Dark lines will appear in spectra of such light, an absorption spectrum
The pattern of dark lines in the absorption spectrum tells us what the cool gas is made of.