Class 6th Ncert Geography Notes -ch-3 PDF Notes Chapter wise

//Class 6th Ncert Geography Notes -ch-3 PDF Notes Chapter wise

Class 6th Ncert Geography Notes -ch-3

Ncert Geography Notes -ch-3 – Motions of the Earth

  • Hello readers as you know that the earth has two types of motions, namely rotation and revolution. Rotation is the movement of the earth on its axis.
  • The movement of the earth around the sun in a fixed path or orbit is called Revolution.
  • The axis of the earth which is an imaginary line, makes an angle of 66½° with its orbital plane.
  • The plane formed by the orbit is known as the orbital plane.
  • The earth receives light from the sun. Due to the spherical shape of the earth, only half of it gets light from the sun at a time .
  • The portion facing the sun experiences day while the other half away from the sun experiences night.
  • The circle that divides the day from night on the globe is called the circle of
    illumination.
  • . The earth takes about 24 hours to complete one rotation around its axis. The period of rotation is known as the Earth day.
  • This is the daily motion of the earth.
  • The portion of the earth facing the sun would always experience day, thus bringing continuous warmth to the region.
  • The other half would remain in darkness and be freezing cold all the time.

Revolution

  • The second motion of the earth around the sun in its orbit is called revolution.
  • It takes 365¼ days (one year) to revolve around the sun.
  • We consider a year as consisting of 365 days only and ignore six hours for the sake of convenience.
  • Six hours saved every year are added to make one day (24 hours) over a span of four years.
  • This surplus day is added to the month of February.
  • Thus every fourth year, February is of 29 days instead of 28 days.
  • Such a year with 366 days is called a leap year.
  •  it is clear that the earth is going around the sun in an elliptical orbit.
  • Notice that throughout its orbit, the earth is inclined in the same direction.
  • A year is usually divided into summer, winter, spring and autumn.

Summer Solstice.

  • You will see that on 21st June, the Northern Hemisphere is tilted towards the sun.
  • The rays of the sun fall directly on the Tropic of Cancer.
  • As a result, these areas receive more heat.
  • The areas near the poles receive less heat as the rays of the sun are slanting.
  • The North Pole is inclined towards the sun and the places beyond the Arctic Circle experience continuous daylight for about six months.
  • Since a large portion of the Northern Hemisphere is getting light from the sun, it is summer in the regions north of the equator.
  • The longest day and the shortest night at these places occur on 21st June.
  • At this time in the Southern Hemisphere all these conditions are reversed.
  • It is winter season there. The nights are longer than the days.
  • This position of the earth is called the Summer Solstice

Winter Solstice

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  • On 22nd December, the Tropic of Capricorn receives direct rays of the sun as the South Pole tilts towards it.
  • As the sun’s rays fall vertically at the Tropic of Capricorn (23½° S), a larger portion of the Southern Hemisphere gets light.
  • Therefore, it is summer in the Southern Hemisphere with longer days and shorter nights.
  • The reverse happens in the Northern Hemisphere.
  • This position of the earth is called the Winter Solstice.
  • Do you know that Christmas is celebrated in Australia in the summer season?

Equinox

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  • On 21st March and September 23rd, direct rays of the sun fall on the equator.
  • At this position, neither of the poles is tilted towards the sun; so, the whole earth
    experiences equal days and equal nights.
  • This is called an equinox.
  • On 23rd September, it is autumn season in the Northern Hemisphere and spring season in the Southern Hemisphere.
  • The opposite is the case on 21st March when it is spring in the Northern Hemisphere and
    autumn in the Southern Hemisphere.
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