Physics of Rainbows Essay -- physics rainbow rainbows

When the Sun's light is refracted on passing through tiny rain droplets falling in the air a Rainbow is formed. Rainbows only need light from the sun or the moon and a large amount of spherical raindrops to form in the atmosphere. The rainbows can be compared to mini prisms. The light is refracted ("bending of light as it passes from one medium to another") and it causes different wavelengths (or colors) of the white light to separate. Whether these wavelengths of light will pass through the raindrop or reflect depends on the angle the light strikes the back of the raindrop. If a wavelength of the light strikes the back of the raindrop at an angle less than 48 degree relative to the normal then the light will pass through the raindrop. However, if the light strikes the back of the raindrop at an angle greater than 48 degrees then the light will be reflected. The reflected light is refracted as it exits the raindrop, but the color or the wavelength does not change. This process is repeated for a large number of raindrops, and a rainbow is formed. It's interesting to note, that the observer has his back to the sun and is facing the raindrops when viewing a rainbow. Thus geometry needs to be just right between the observer,the place where it is raining, and the sun. The light from the sun passes over the observer, strikes rain droplets, and comes back to the observer. Yet, the Earth prevents us to see the whole arc of a rainbow. When the sun is higher in the sky, only a small arc of a rainbow cab be seen from land. The reason for that is that the arc cannot be followed below the horizon(the droplets in the air below the horizon cannot be seen). It is possible to see the full arc of rainbow when flying above the clouds in an airp... ...r than than the rainbow produced by direct light. Another type of reflective rainbow can be seen on water surfaces like puddles or ponds. After a heavy rainfall, there are lots of spherical floating on a water surface. Therefore, it ispossible for a rainbow to be formed from indirect light rays. One of the main sources of light is from light, which is reflected back of a water surface, such as a lake or ocean. If we look at two raindrops, the first contributes to the rainbow formed by rays direct from the sun, and the other drop contributes to the rainbow formed by the indirect rays (the one which are reflected off the water surface). The rays leaving both of the drops leave at 42 degrees to the paths at which they entered. Thus, it is clear that a rainbow produced by a reflected light source will appear higher in the sky than one formed by direct sunlight.