A spherical black body with a radius of 12 cm radiates 450 W power at 500 K . If the radius were halved and…

A spherical black body with a radius of 12 cm radiates 450 W power at 500 K. If the radius were halved and the temperature doubled, the power radiated in watt would be
  1. 225
  2. 450
  3. 1000
  4. 1800

Solution

By Stefan's law rate of heat radiation from a black body =σAT4
⇒ Rate of power loss
r∝R2 T4
r1r2=R12 T14R22 T24
=4×116
450r2=14
r2=1800 watt ~

Asked in: NEET 2017

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