I remember solid state physics courses where the topic was the band gap of semiconductors. In Silicon semiconductors, the electrons can be brought from the lower to the higher energy band via thermal energy. When the electrons go back to the lower energy band, this energy is release, also in the form of heat (thermal energy).
In GaP semiconductors though, this is optical energy. 😱
So, which would you rather have it? A Powerbook G8 where you suffer 3rd degree burns when you move the mouse, or a Powerbook G8 where you have to wear sunglasses. 😎