A) \[S\propto {{T}^{4}}\]
B) \[S\propto {{T}^{2}}\]
C) \[S\propto {{\theta }^{2}}\]
D) \[S\propto {{\theta }^{2}}\]
Correct Answer: A
Solution :
Let radius of sun = R Distance of earth from the sun\[=d\] Power radiated from the sun \[=(4\pi {{R}^{2}})\sigma {{T}^{4}}=P\] Energy received/area/s \[S=\frac{P}{4\pi {{d}^{2}}}\] \[=4\pi {{R}^{2}}\sigma \frac{{{T}^{4}}}{4\pi {{d}^{2}}}=\sigma {{T}^{4}}\frac{{{R}^{2}}}{{{d}^{2}}}\] \[=\frac{1}{4}\sigma {{T}^{4}}{{\left( \frac{2R}{d} \right)}^{2}}\] Angle subtended by sun at earth \[\alpha =\frac{2R}{d}\] \[S=constant\times {{T}^{4}}\times {{\alpha }^{2}}\] \[S\propto {{T}^{4}}\]
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