A) \[{{e}_{x}}>{{e}_{y}}\And \,\,\,{{a}_{x}}<{{a}_{y}}\]
B) \[{{e}_{x}}<{{e}_{y}}\And \,\,\,{{a}_{x}}>{{a}_{y}}\]
C) \[{{e}_{x}}>{{e}_{y}}\And \,\,\,{{a}_{x}}>{{a}_{y}}\]
D) \[{{e}_{x}}<{{e}_{y}}\And \,\,\,{{a}_{x}}<{{a}_{y}}\]
Correct Answer: C
Solution :
Rate of cooling \[\left( -\frac{dT}{dt} \right)\ \propto \] emissivity (e) From graph, \[{{\left( -\frac{dT}{dt} \right)}_{x}}>{{\left( -\frac{dT}{dt} \right)}_{y}}\] Þ \[{{e}_{x}}>{{e}_{y}}\] Further emissivity (e) µ Absorptive power Þ \[{{a}_{x}}>{{a}_{y}}\] (\[\because \] good absorbers are good emitters).
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