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Q84 (CAPF/2009) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Thermal physics Answer Verified

Consider the following statements : 1. The Earth receives the Suns energy at the infrared end of the spectrum. 2. The Earth re-radiates the Suns heat as ultraviolet energy. Which of the above statements is/are correct ?

Result
Your answer: —  Â·  Correct: D
Explanation

Statement 1 is incorrect because the Sun's energy (insolation) is primarily received as shortwave radiation, which includes visible light and ultraviolet radiation, rather than being concentrated at the infrared end [c1][c2]. While the Sun does emit infrared radiation, the peak of its emission is in the visible spectrum [t4]. Statement 2 is incorrect because the Earth, being much cooler than the Sun, re-radiates energy as longwave radiation, specifically in the infrared part of the spectrum, not ultraviolet [c1][c4]. Terrestrial radiation consists almost entirely of infrared wavelengths [t1][t2]. This distinction between incoming shortwave solar radiation and outgoing longwave terrestrial radiation is fundamental to the Earth's heat budget and the greenhouse effect [c2][c3]. Therefore, both statements are scientifically inaccurate regarding the primary spectral bands of incoming and outgoing energy.

Sources

  1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 21: Horizontal Distribution of Temperature > Insolation > p. 282
  2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 21: Horizontal Distribution of Temperature > 21.5. Heat Budget > p. 293
  3. [3] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 17: Climate Change > Emission > p. 255
  4. [4] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Greenhouse Effect and Global Warming > p. 7
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