Page 109 - SST Class 06

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Earth in the Solar System

If you look at the sky above you, during the night Glass
prism
time, you’ll notice that it is full of tiny shining White Screen
objects. Some of these objects are bright while Light Red
others are dim. Most of them, seem to be twin- Orange
Yellow
kling. The reality is not all of the objects in the Dispersion of Light Green
sky can be seen with the naked eyes. It is our Blue
Indigo
solar system which is full of these objects. So let’s Violet
study about the solar system in detail.
When white light shines through a prism, the
STARRY SKY
light is separated into all its colours. A prism is a
The sky is what you see, when you look upwards, specially shaped crystal.
in an open space, when you’re on a planet or a
Like energy passing through the ocean, light
moon. Clouds are in the sky, but so are stars and
energy travels in waves, too. Some light travels in
galaxies as well as the sun and the moon. short, "choppy" waves. Other light travels in long,
A kite is said to be flying in the sky when it is lazy waves. Blue light waves are shorter than red
about 300 m high. In general, it goes from about light waves.
300 m upwards or even sideways, without limit.
Visible Lights

Red
Orange
Yellow
Green

Blue

All light travels in a straight line unless something
gets in the way and does one of these things:
If you’re not on a planet or a moon, then there is g reflect it (like a mirror)
no sky. You would simply see space, in all direc- g bend it (like a prism)
tions.
g or scatter it (like molecules of the gases in
the atmosphere)

Sunlight reaches the Earth’s atmosphere and is
It’s easy to see that the sky is blue. Have you ever
wondered why? scattered in all directions by all the gases and
particles in the air. Blue light is scattered in all
The light from the sun looks white. But it is really directions by the tiny molecules of air in the
made up of all the colours of the rainbow. Earth’s atmosphere. Blue is scattered more than

Social Science-6 109