I- Spectrum

When the light crosses a surface like  a prism glass, rain , a disk, it's decomposed  in the colors of rainbow (purple, blue, green,yellow,orang,red)

Prism: the crossing of the light in the prism allows the decoposition of the light

Rainbow: The water drops of the rain allow the decomposition of the light too

Spectrum of the light: It's the result of the decomposition of the light

Disk: We can see the colors because of the reflect of light on the disk

II-Gaseous spectrum

A gaseous spectrum allows the indentification of chimicals elements in a gas, it's represented by colors stripes on a black background

  Sodium (Na)

Mercury(Hg)

 

III-Absorption spectrum

An absorption spectrum of a substance is a spectrum got after the crossing  on the substance by the light

Sodium(Na)

Mercury(Hg)

The stripes of gaseous spectra are similar to the stripes of absorption spectrum on a chemical element

Lithium

IV-Stars spectrum

The gaseous and absorptions spectra allow theidentification chimical elements in the star's atmosphere

Example

Sun