A rainbow is one of the most beautiful phenomena of nature, and people have long thought about its nature. Even Aristotle, the Greek philosopher, tried to explain the cause of the rainbow.
Solar beam or an ordinary beam of white light is actually a combination of all colors. You probably noticed what happens when a ray of light falls on the beveled edge of the mirror or on the surface of the bubble. A ray of white light splits into various colors. We will see red, orange, yellow, green, blue and purple.
To see a rainbow, the observer must stand between the Sun and the raindrops, in which the refraction of sunlight back to the Sun. As the colored rays emerge from the droplet at different Angles, it is clear that from each drop in the eye of the observer may get only a single colored beam. The rest of the rays coming from the same drop, the observer will not see, pass by his eyes — above or below.
The brightness of the rainbow depends on the number of water droplets in the air and their sizes. It was found that the larger the raindrops, the brighter the rainbow. That is why the rainbow is particularly bright during a brief summer rain, when the earth falls out frequent large drops. It is also noticed that depending on the size of the droplets is changed, and the rainbow — changes the brightness and width of the individual strips. So, the droplets with a diameter from 0,5 up to 1 millimetric rainbow of bright purple and green stripes and with a very weak blue band. When the size of the droplets is much smaller in the rainbow are not clearly visible red band, and more yellow. For example, droplets with a diameter of 0.1 millimeter and a few less give a bright beautiful rainbow, a bit wider than usual, in which pure red is not at all. If in the rainbow clearly visible white stripe, it means that the amount of raindrops does not exceed 0.03 fraction of a millimeter.