Spectroscopy Lab Suite - LEDs

Now, open up the Spectroscopy Lab Suite Program and select LEDs.

Move an LED from the bottom left hand corner of the screen into the LED holder between the positive and negative ends of the battery. Click on add conduction band and then add valence band. Two bands should appear on the energy diagram on the right hand size of the screen. First move the conduction band up and down. What changes do you see in the variable spectrum below the spectrum produced by a particular color LED?

Now try moving the valence band up and down. What differences do you see now?

While paying attention to the output spectrum, now move both the valence band and conduction band arbitrarily. Do you see a correlation?

The width of the gap between the two main energy bands, valence band and conduction band, determines the color that particular LED emits. Conduction band, the one with the highest energy, contains electrons that cannot leave the solid but are not firmly attached to any atom. They can move throughout the solid. Valence band contains electrons bound to their respective atoms more strongly and are unable to break free from the atoms.

How does changing the width of the bands affect the output spectrum?