1. Electrons and the Visible Spectrum

2. In the Bohr model it was the existence of colour that showed there were different energy levels. In the Bohr model it was the existence of colour that showed there were different energy levels. Ground state – the lowest energy state of an electron Ground state – the lowest energy state of an electron Excited state - an electron at a high higher level than the ground state. Excited state - an electron at a high higher level than the ground state.

3. Colour and Metal Ions When heat or electricity is added to a metal some of the electrons become excited and leave the ground state to jump to a higher energy level. When heat or electricity is added to a metal some of the electrons become excited and leave the ground state to jump to a higher energy level. The electrons will eventually fall back to their ground state and will release their energy either as heat or light. The electrons will eventually fall back to their ground state and will release their energy either as heat or light. The frequency of this released energy determines the colour we see. The frequency of this released energy determines the colour we see.

4. The larger the jump (and fall) the higher the frequency we see. A low frequency light may be produced by a fall from the 2 nd level to the 1 st and a high frequency may be produced with a fall from the 6 th level to the 2 nd. The larger the jump (and fall) the higher the frequency we see. A low frequency light may be produced by a fall from the 2 nd level to the 1 st and a high frequency may be produced with a fall from the 6 th level to the 2 nd. I R  R  O  Y  G  B  I  V  UV I R  R  O  Y  G  B  I  V  UV Low frequency High Frequency Low frequency High Frequency

5. Examples Fireworks Fireworks Flares Flares

6. Light Bulb – Light Bulb – (Tungsten) (Tungsten) Fire Logs - Fire Logs -

7. Neon Signs – Neon Signs – Street Lights – Street Lights – (Sodium Lamp) (Sodium Lamp)

8. Mercury Vapour Lamp Mercury Vapour Lamp