1. Tardigrade
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  3. Physics
  4. The radiant energy from the sun, incident normally at the surface of earth is 20 kcal/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 ?

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Q. The radiant energy from the sun, incident normally at the surface of earth is 20 kcal/$m^2 \, min.$ What would have been the radiant energy, incident normally on the earth, if the sun had a temperature, twice of the present one ?

AIPMTAIPMT 1998

Solution:

$E= \sigma T^4=20. \, \, T'=2T $
$\therefore \, E'=\sigma (2T)^4=16\, \sigma T^4$
$\, \, \, \, =16 \times 20=320 \, k \, cal/m^2 \, min $