`=>C`

`=>B`

→ The metal ions in the solution gain energy from the components of the flame and are electronically excited, ie electrons are promoted to higher energy states.

→ The electrons fall back to lower energy states, releasing energy as photons.

→ The lines observed through the spectroscope are therefore emission lines. Because the electron energies are quantised, and transitions between states are restricted to well-defined energies, the energy released is well defined, thus the emission is seen as lines and not a continuous spectrum.

→ Line A is the blue end of the spectrum, meaning the transition is of high energy (shorter wavelength).

→ Line B is at the red end of the spectrum, meaning the transition is of low energy (longer wavelength).