If you arrived here by clicking on a hyperlink in that article, you can return to that point by using the BACK function of your browser program. Although light travels mostly in straight lines, it can also be scattered by particles such as air molecules, meaning that portions of the light energy are sent off in various directions. For our atmosphere, this effect is strongest in the shortest wavelengths, decreasing almost to 0 at the red wavelengths. For a more detailed explanation, take a look at this web site in Australia . Photons are particles of energy that can be absorbed into and emittted from atoms and molecules.
Lasers are possible because of another type of photon emission called stimulated emission.
But when light from the laser is passed through two closely-spaced pin holes, the resulting interference pattern is similar to the pattern of ripples seen when two rocks are dropped into water to form interfering water waves. The laser light clearly acts like a wave in many respects. Yet it is the same light. Wavefronts and rays Wave fronts from a point source are spherical surfaces of constant phase. Rays are lines that are normal to these wavefronts, showing the direction of energy flow at one particular point.