First slide

Radiation

Question

The rectangular surface of area 8cm × 4cm of a black body at a temperature of 127⁰C emits energy at rate of E per second. If the length and breadth are reduced to half of its initial value and the temperature is raised to 327⁰C, the rate of emission of energy will be

Moderate

A

$\large \left ( \frac {3E}{8} \right )$
B

$\large \left ( \frac {9E}{16} \right )$
C

$\large \left ( \frac {81E}{16} \right )$
D

$\large \left ( \frac {81E}{64} \right )$

Solution

l₁ = 8cm, b₁ = 4cm; l₂ = cm, b₂ = 2cm
T₁ = 127⁰C = 400k, T₂ = 327⁰C = 600k
$\large \frac {E_2}{E_1}=\left ( \frac {T_2}{T_1} \right )^4\left ( \frac {l_2b_2}{l_1b_1} \right )$
$\large \frac {E_2}{E}=\left ( \frac {600}{400} \right )^4\left ( \frac {4\times 2}{8\times 4} \right )$
$\large E_2=\frac {81}{64}E$

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