Do you
know the sky is blue ?
Light is a kind
of energy that travels through space.
The
light we can see is just a part of the electromagnetic spectrum,
an image of colors as seen in a rainbow.
The
light may look white, but it is actually a combination of these
colors.
 The colors of the spectrum are red, orange,
yellow, green, blue, indigo and violet, respectively. Each color
has a different wavelength, frequency and energy. Red has the
longest wavelength and the lowest frequency and energy. Violet
has the shortest wavelength and the highest frequency and energy.
As
light moves, it travels in a straight line until it reaches some
obstacles. When it reaches particles larger than the wavelength
of visible light, such as dust or gas molecules, it gets reflected
in different directions. The light appears white because it still
contains all of the same colors.
When
light hits gas molecules, which are smaller, some of it may get
absorbed and then radiated. The higher frequencies (blues) are
absorbed more often than the lower frequencies (reds). The absorbed
blue light is then radiated in different directions and gets
scattered in the sky. When we look to the sky, we see the blue
light scattered in every direction, so it looks blue.
In
outer space, the sky looks black instead of blue because there
is no atmosphere, so light travels in a straight line and does
not reach any obstacle, thus it does not get scattered.
 On Earth, when we
look at the Sun, it appears yellow, but it looks white in outer
space. This is also because there is no atmosphere to scatter
the Sun's light. On Earth, the blues and the violets are removed
from the direct rays of the Sun and all the remaining colors
together appear yellow. |
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