- All the materials are made up of atoms and molecules. These atoms and molecules possess certain fixed energy.
- An atom or molecule having lowest possible energy is said to be in ground state.
- When we heat the materials the electrons of these atoms gain energy and move into excited states (higher energy state).
- An atom of molecule in excited state can emit light to lower its energy in order to get stability and come back to ground state.
- Light emitted in such process have certain fixed wavelength for one kind of atoms.
- The light emitted by different kinds of atoms are different because the excited states electrons will go are different. So different elements produce different flame colours.