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Q39 (IAS/2013) Geography › World Physical Geography › Earth rotation and time Answer Verified

Variations in the length of daytime and nighttime from season to season are due to

Result
Your answer: —  Â·  Correct: D
Explanation

Variations in the length of daytime and nighttime from season to season are primarily caused by the revolution of the Earth around the Sun on a tilted axis [4]. The Earth's axis is inclined at an angle of 66.5 degrees to the plane of the ecliptic (or 23.5 degrees from the perpendicular) [1]. This fixed tilt, combined with the Earth's orbital motion, means that different hemispheres are tilted toward or away from the Sun at different times of the year [3]. When a hemisphere is tilted toward the Sun, it experiences longer daylight hours (summer), while the hemisphere tilted away experiences shorter days (winter). While the Earth's rotation creates the basic 24-hour day-night cycle, it is the interaction between the axial tilt and the revolution that drives the seasonal variation in day length [2].

Sources

  1. [1] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 2: The Earth's Crust > The Earth's Revolution > p. 6
  2. [4] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 19: The Motions of The Earth and Their Effects > Lunar Nodal Cycle > p. 266
  3. [3] Science-Class VII . NCERT(Revised ed 2025) > Chapter 12: Earth, Moon, and the Sun > 12.2.2 Seasons on the Earth > p. 177
  4. [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 12: Earth, Moon, and the Sun > In a Nutshell > p. 184
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