Page 13 - K-2185 S.St (Final) 28-04-18 1C P70 LITE

and the Earth, it blocks the path of rays of the Sun totally or partially
falling on the Earth. The Earth experiences the shadow of the Moon.
This is known as the solar eclipse. It occurs only during a New Moon.
(h) The Earth revolves around the Sun. It is called revolution. During
revolution, when the Earth passes between the Sun and the Moon,
it casts its shadow on the Moon. It may be partial or totally dark.
This is known as the lunar eclipse. A lunar eclipse can last up to an
hour and a half. During a lunar eclipse, the Moon may turn reddish.

Moon’s orbit

Earth’s orbit

Sun Earth Moon

Lunar Eclipse

(i) Lengths of days and nights vary due to the rotation of the earth
and its tilting about the axis towards or away from the Sun. During
summer, the days are long and nights are short. The hemisphere
which is tilted towards the Sun experiences summer and gets longer
days and shorter nights. In the northern hemisphere, 21st June is the
longest day. After that the length of the day goes on decreasing. In
the northern hemisphere, 22nd December has the shortest day and
the longest night.

(j) There are four main seasons on the Earth. They are – summer,
winter, autumn and spring. Seasons are formed due to the revolution
movement of the earth.

The Earth rotates around the imaginary tilted axis. The tilt of the
axis and the revolution of the Earth cause change in seasons.

On 21st June, the northern hemisphere is tilted towards the Sun.
The sunrays fall directly on the Tropic of Cancer in the northern
hemisphere at this time. The northern hemisphere thus experiences
summer.

At the same time, the southern hemisphere is tilted away from the
Sun. Thus, it experiences winter.

On 22nd December, the seasons in the two hemispheres are reversed.
Now, the northern hemisphere is tilted away from the Sun and
experiences winter. On the other hand, the southern hemisphere is
now tilted towards the Sun. Thus, it experiences summer.

(k) Formation of day and night is caused by rotation of the Earth. The
part of the Earth facing the Sun receives sunlight. Then it is said
that part has ‘daytime’ or ‘day’. As the Earth continues to rotate,
the areas facing the Sun gradually moves away and the other areas

Social Science (13) Class–5