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Lesson -4 (Motions of the Earth), , Written, , 4, (1) Equinox (2)rotation (3) 4 years (4) 366days (5) Finland (6) 231/2°, , 2., 3., , (1), , orbit (2) aphelion(3) elliptical (4) summer solstice (5) rotation, , Rotation Revolution, , Movement of the earth on its ‘ (i). The movement of earth around the sun, own axis from west to east is called revolution., , is called rotation., , The earth takes 24 hrs. to (ii) The earth takes 365 days and 6 hrs., , to complete one rotation. to complete one revolution., , Atthe equator the earths speed (iii) The earth revolves in the anti-clockwise, of rotation on it's axis is 1600 direction at the speed of about, , Km/hr. / 1,00,000 km./hr., , The seasons are caused due to inclination of Earth's axis and Earth's revolution around, sun. . :, , There are no seasons at the equator for the following reason, (i) Atequatorsun rays always fall vertically overhead., , (i) Sunrays concentrated on small areas., , (iii) The sunrays come directly on equator that's why it is having long and hot summer., , The rays of sun fall vertically at equator that is why day and night are equal everywhere on, 21" march and 23” september., , After every four years, the 6 hours add up to the fourth year so that it has 366 days. This, additional day is added to the month of february of fourth year. The february month of that, year has 29 days. While the year has 366 days. Such a year is called leap year and extra, day is called leap day., , The length of the day and night varies because of inclination of the Earth's axis., , The effects of rotation are - (i) Occurrence of day and night., , (i) Wecan come to know about directions due to the sun rise and sunset., , (iii) The sun appears to move from the east to the west due to the rotation of the earth.

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The following are the effects of revolution- (i) Cycle of seasons, , (ii) Temperature zohes over the earth. (iii) Variations in the length of the days and nights., Book page no. 55 (Diagram), , Season changes because of combined effect of revolution of the earth and inclination of, earth's axis in the same directions. That's why there are four seasons in a year- spring,, winter, summer and autumn., , The rotation of the earth causes the phenomenon of day and night. But days and nights are, not of same length. This is due to inclination of the earth's axis.