Rainbow

The rainbow is one of the nicest natural phenomena. During years it was associated with misfortunes or catastrophes, due to the fact that any change in the weather was perceiving with the influence of the gods, as if they were signs sent by them.

Rainbow. San Juan de la Rambla. Photography realized by Yaiza Quintero González.

This phenomenon has a physical explanation, but first it is necessary to understand the concept of rainbow from the scientific point.

This one is a spectrum of light in which the “seven colors " are decomposed and observed at a glance.

If someone asks us; how many colors are really in the rainbow? We will answer that about seven, those that we see and we can count. But it is not a right answer, you have read it well, the rainbow is not composed by seven colors, the same one has thousands of them.

Isaac Newton was the first one that explained the separation of colors in the white light with the experiment of a prism (already it was spoken about it in another paragraph). After realizing the above mentioned experiment, it was determined that the light was composed by seven colors, to continue with the rule of the seven.

Rule of the seven, what does it mean? In the ancient time it was thought that the seven was a number with a strong superstition and mysticism. To understand it better, seven was the number of the perfection since seven planets existed; seven musical notes; seven days of the week; seven properties of the minerals were known... 

What is the fisiefecto of the rainbow? When the light beam enters the surface of the rain drop, the light refracts, that is to say, the colors that compose the white light suffer a separation, being able to be visible. On having gone out of these, of the drops, they suffer a new refraction that increases moreover the separation between colors.

A necessary condition, apart from the water vapor in the air, is that the Sun will be to our back, in order that these beams form angles of 138 º to form an arch.

Refraction and Reflection of a bundle of light in a water drop.

The question can always arise; why we do not see the complete arch? Because the soil prevents that we observe the other half of this arch. In some occasion it is possible to observe it, for example in the edges of a waterfall.

Finally to emphasize, every rainbow is unique, due to the position in which someone is placed to observe it.  We can see it in different shapes and colors. So, none of us won´t see the same rainbow, and on having seen every rainbow, you can feel satisfied,  you never will see the same one in the whole life, nobody except you will be able to see this rainbow.

The nature shows us many curious and nice phenomena, they can be understood and explained through The Physics.

Bibliography:

http://goo.gl/znhyL8

http://goo.gl/OVLnPy