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