Q43. Why is the greenhouse effect important?
Carbon dioxide released in the atmosphere creates a greenhouse effect by
trapping the heat radiated from the earth. It is therefore called a greenhouse
gas and without it the earth would have been too cold to live in.
Q44. Why amount of insolation decreases from equator towards
Sun rays falls almost vertically on the equator and covers less space whereas
sun rays falls at slanting angle on the poles and covers more space. Thus, the
amount of insolation decreases from the equator towards the poles.
Q45. How air circulation takes place?
air is heated, it expands, becomes lighter and goes up. Cold air is denser and
heavy. That is why it tends to sink down. When hot air rises, cold air from surrounding
area rushes there to fill in the gap. That is how air circulation takes place.
Q46. Air above us presses us with a great force on our bodies.
However, we don’t even feel it. Why?
Air above us presses us with a great force on our bodies. However, we don’t even
feel it. This is because the air presses us from all directions and our body
exerts a counter pressure.
Q47. Why do astronauts wear space suits on the moon?
Astronauts have to wear special protective space suits filled with air when
they go to the moon. If they did not wear these space suits, the counter
pressure exerted by the body of the astronauts would make the blood vessels
burst. The astronauts would bleed.
Q48. Why temperature in cities much higher than that of
in cities is much higher than that of villages because
The concrete and metals in buildings and
the asaphalt of roads get heated up during the day. This heat is released
during the night.
Also, the crowded high rise buildings of
the cities trap the warm air and thus raise the temperature of the cities.
Q49. Why is the atmosphere essential for life?
living beings on this earth depend on the atmosphere for their survival. It provides
us the air we breathe and protects us from the harmful effects of the sun’s rays.
Without this blanket of protection, we would be baked alive by the heat of the
sun during day and get frozen during night. So it is this mass of air that has
made the temperature on the earth liveable.
Q50. What are the harmful effects arising from the greenhouse
its level in the atmosphere increases due to factory smoke or car fumes, the
heat retained increases the temperature of the earth. This is called global
warming. This rise in temperature causes the snow in coldest parts of the world
to melt. As a result the sea level rises, causing floods in the coastal areas.
There may be drastic changes in the climate of a place leading to extinction of
some plants and animals in the long run.
Q51. Discuss the importance of stratosphere?
Above the troposphere lies the
stratosphere. It extends up to a height of 50 km. This layer is almost free
from clouds and associated weather phenomenon, making conditions most ideal for
One important feature of stratosphere is
that it contains a layer of ozone gas which protects us from the harmful effect
of the sun rays.
Q52. What is the composition of the atmosphere?
air we take in while breathing is actually a mixture of many gases. Nitrogen
(78%) and oxygen (21%) are two gases which make up the bulk of the atmosphere.
Carbon dioxide (O.3%), helium, ozone, argon (0.93%) and hydrogen are found in
lesser quantities. Apart from these gases, tiny dust particles are also present
in the air. The pie chart gives you the percentage of different constituents of