Rainbow – one of those unusual optical phenomena with which the nature sometimes pleases the person. For a long time people tried to explain emergence of a rainbow. The science considerably approached understanding of process of emergence of the phenomenon when in the middle of the 17th century the Czech scientist Mark Martsi found out that the light beam is non-uniform on the structure. A bit later Isaac Newton studied and explained the phenomenon of dispersion of light waves. As now it is known, the light beam refracts on border of two transparent environments having various density.
Instruction
1. As Newton established, the white light beam turns out as a result of interaction of beams of different color: red, orange, yellow, green, blue, blue, violet. Every color it is characterized by a certain wavelength and frequency of fluctuations. On border of transparent environments the speed and length of light waves change, the frequency of fluctuations remains the same. Every color has own index of refraction. Least of all from the former direction the beam of red color, slightly more orange, then yellow, etc. will take the leave. The largest index of refraction has a violet beam. If on the way of a light beam to establish a glass prism, then it not only will deviate, but also will break up to several beams of different color.
2. And now about a rainbow. In the nature the glass prism is served by rain drops which sunshine when passing through the atmosphere face. As density of water is more than density of air, the light beam on border of two environments refracts and decays on components. Further color beams move already in a drop before collision with its opposite wall which is also border of two environments, and, besides, has mirror properties. The most part of a light stream after secondary refraction will continue the movement in the air environment behind rain drops. Some of its part will be reflected from a back wall of a drop and will leave on air Wednesday after secondary refraction on its front surface.
3. This process happens in a set of drops at once. To see a rainbow, the observer has to stand a back to the Sun and facing a rain wall. Spectral beams leave rain drops under different corners. From each drop only one beam gets into an eye of the observer. The beams leaving the next drops merge, forming a color arch. Thus, from the topmost drops beams of red color get into an eye of the observer, from those that below – orange, etc. Violet beams will most strongly take the leave. The violet strip will be lower. It is possible to see a rainbow in the form of a semicircle when the Sun is at an angle no more than 42 ° concerning the horizon. The above the Sun rises, the it is less rainbow sizes.
4. Generally, the described process is slightly more difficult. The light beam in a drop is reflected repeatedly. At the same time not one color arch, but two – a rainbow of the first and second order can be observed. The external arch of a rainbow of the first order is painted in red color, internal – in violet. At a rainbow of the second order on the contrary. It looks is usually one many more pale than the first as at repeated reflections the intensity of a light stream decreases.
5. Much less often in the sky three can be observed, four and even five color arches at the same time. Similar was observed, for example, by residents of Leningrad in September, 1948. This results from the fact that the rainbow can arise as well in the reflected sunshine. Such repeated color arches can be observed over the extensive water surface. At the same time the reflected beams go from below up, and the rainbow can "be turned upside down".
6. Width and brightness of color strips depend on the sizes of drops and on their quantity. Drops with a diameter about 1 mm give wide and bright violet and green strips. The more small than a drop, the red strip is allocated more weakly. Drops with a diameter about 0.1 mm do not give a red strip at all. The droplets of water vapor forming fog and clouds do not form a rainbow.
7. It is possible to see a rainbow not only in the afternoon. A night rainbow - quite unusual occurrence arising after a night rain aside, the opposite Moon. The intensity of color of a night rainbow is much weaker day.