Question

the 13th question.

urgent please

Answer 1

Stephen's law :-

The principle that the energy radiated per second by unit area of a black body at thermodynamic temperature T is directly proportional to T4. The constant of proportionality is the Stefan constant, equal to 5.670400 × 10–8 Wm–2 K–4. Also called: Stefan-Boltzmann law.

Answer 2

Stefan - Boltzmann Law

This law states that "the total electromagnetic energy radiated by a body at absolute temperature T is proportional to its size, its able to radiate called emissivity and to its temperature."

For a body which is a perfect radiator, the energy emitted per unit time (power) is given by,

$\dfrac {\Delta H}{\Delta t}=A\sigma T^4$

where $A$ is the area and $T$ is the absolute temperature of the body. This relation obtained experimentally by Stefan and later proved theoretically by Boltzmann is known as Stefan - Boltzmann law and the constant $\sigma$ is called Stefan - Boltzmann constant, whose value in SI units is $5.67\times 10^{-8}\ W\ m^{-2}\ K^{-4}.$

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In the problem, we are given,

$T=2\times 10^3\ K\\\\\\A=2\times 10^{-4}\ m^2\\\\\\\Delta t=10\ min=6\times 10^2\ s$

Then, by Stefan's Law,

$\Delta H=A\sigma T^4\ \Delta t\\\\\\\Delta H=2\times 10^{-4}\times 5.67\times10^{-8}\times(2\times 10^3)^4\times 6\times 10^2\\\\\\\large\underline {\underline {\Delta H=108864\ J}}$