First slide

Radiation

Question

A sphere of 3 cm radius acts like a black body. If it is in equilibrium with its surroundings and absorb 30 k watt of energy radiated to it from the surrounding. Then the temperature of the sphere will be

Moderate

A

816 K
B

916 K
C

1616 K
D

2616 K

Solution

Radius of sphere r = 3 cm = 0.03 m The energy absorbed
E = 30 kW = 30 $\times 10^{3} watt$
Energy absorbed by black body when the temperature of surroundings is T, is given by
E = ${σAT}^{4}$
or $30 \times 10^{3} = 5.672 \times 10^{- 8} \times 4 π {(0.03)}^{2} \times T^{4}$
$30 \times 10^{3} = 0.64 \times 10^{- 8} \times T^{4}$
$T^{4} = \frac{30 \times 10^{3}}{0.064 \times 10^{- 8}} = 46.875 \times 10^{12}$
= 2.616 $\times 10^{3} = 2616 K$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App