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 ?

Question

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 ? (A) 320 k cal/m2 min (B) 40 k cal/m2 min (C) 160 k cal/m2 min (D) 80 k cal/m2 min

Tardigrade Admin · Accepted Answer

E= σ T4=20. T'=2T ∴ E'=σ (2T)4=16 σ T4 =16 × 20=320 k cal/m2 min

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 ?

$320 k c a l / m^{2} min$

$40 k c a l / m^{2} min$

$160 k c a l / m^{2} min$

$80 k c a l / m^{2} min$

$E = σ T^{4} = 20. T^{'} = 2 T$
$∴ E^{'} = σ (2 T)^{4} = 16 σ T^{4}$
$= 16 \times 20 = 320 k c a l / m^{2} min$

Q. The radiant energy from the sun, incident normally at the surface of earth is 20 kcal/m2min. What would have been the radiant energy, incident normally on the earth, if the sun had a temperature, twice of the present one ?

320kcal/m2min

40kcal/m2min

160kcal/m2min

80kcal/m2min