Explanation
False
Explanation:
Radiation heat transfer is the technique of transferring heat from one body at higher temperature to another body at lower temperature without affecting the medium.
Transfer of heat by radiation does not need any material medium.
The sun's heat, for example, is transmitted to the earth by radiation.
Correct answer: (iii) upwards
Heat is always transferred vertically upwards through convection.
This occurs because medium particles close to a heat source absorb heat from the source and begin to move faster, so they become farther i.e. the medium expands.
As a result, the density of medium near the source of heat becomes less i.e. it becomes lighter.
The less dense medium rises up and the dense medium from above moves down to take its place.
Thus, a current is set up in the medium which is called a convection current.
let us assume initial Temperature $$T_1=T$$ then final will be
$$T_2=\dfrac{50}{100}T+T=\dfrac{150}{100}T=\dfrac{15}{10}T$$
energy radiated
$$e_1=\sigma A T_1^4\quad \left(1\right)$$
$$e_2=\sigma A T_2^4\quad \left(2\right)$$
$$\%$$ increase in radiation
$$=\dfrac{e_2-e_1}{e_1}\times 100$$
$$=\dfrac{\sigma A T_2^4-\sigma A T_1^4}{\sigma A T_1^4}\times 100$$
$$\dfrac{\left(\dfrac{15}{10}T\right)^4-T^4}{T^4}\times 100$$
$$\dfrac{15^4-10^4}{10^4}\times 10^2$$
$$\dfrac{50625-10000}{10^2}$$
$$=406.25$$
$$\approx 400\%$$
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