Part 1 of Essay
is what we see. It can be thought of either as a particle, (the photon), or as a wave. The photon we can easily think of as a small dot travelling through space at the speed of . Each photon has a particular colour or energy. But how do we think of as a wave? For this we need to know that is also an "Electro-magnetic fi ....

Part 2 of Essay
.... more intense , as well as select of a particular colour (or energy). ¨ travels at a speed of 2.99792458x10^{8} ms^{-1} ¨ When passing though matter, is slowed down by brief interactions, and so appears to travel more slowly. ¨ This "slowing down" is accounted for by the index of refraction of the matter. 's properties can at first seem confusing and inconsistent because of the unique nature of light: light has the properties of both a wave and a particle. In some situations, light's behavior is more easily ....