Thermal Properties of Matter - Result Question 41

42. The radiant energy from the sun, incident normally at the surface of earth is 20kcal/m2 min. What would have been the radiant energy, incident normally on the earth, if the sun had a temperature, twice of the present one?[1998]

(a) 160kcal/m2min

(b) 40kcal/m2min

(c) 320kcal/m2min

(d) 80kcal/m2min

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Answer:

Correct Answer: 42. (c)

Solution:

  1. (c) According to Stefan’s law, ET4

E1E2=T14T24 or 20E2=T424T4

E2=320kcal/m2. min.



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