Question

The temperature of a radiating body increases by 30%. Then the increase in the amount of radiation is

• A. 185%
• B. 285%
• C. 325%
• D. 130%

Answer 1

Answer: (A)

185%

Answer 2

According to Stefan’s law, amount of radiations emitted $E \propto T^{4},$

$\therefore\frac{E`}{E} = \frac{\left\lbrack T + \left( \frac{30}{100} \right)T \right\rbrack}{T^{4}}^{4} = \left\lbrack \frac{130}{100} \right\rbrack^{4} = (1.3)^{4}$

Percentage increases in E

$= \frac{E` - E}{E} \times 100 = \left( \frac{E`}{E} - 1 \right) \times 100$

$= ((1.3)^{4} - 1)100 = 185\%$