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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Physics
Chapter
Thermal Properties of Matter

NTA Abhyas 2020 · Physics · Thermal Properties of Matter

The graph shown in the adjacent diagram represents the variation of...

The graph shown in the adjacent diagram represents the variation of temperature (T)( T ) of two bodies xx and yy having the same surface area, with time (t).Bothofthesebodiesloseheatonlyduetotheemissionofradiation.Findthecorrectrelationbetweentheemissiveandabsorptivepowerofthetwobodies.<br/><br/><imgalt=""src="/api/proxy−image?url=https). Both of these bodies lose heat only due to the emission of radiation. Find the correct relation between the emissive and absorptive power of the two bodies.<br /> <br /> <img alt="" src="/api/proxy-image?url=https%3A%2F%2Ffirebasestorage.googleapis.com%2Fv0%2Fb%2Fquantrexacademy-app.firebasestorage.app%2Fo%2Fquestions%252Ffigs%252Fnta_abhyas%252Fjee_main%252Fimages%252F29201_que.png%3Falt%3Dmedia \text{ and } clean=1 \text{ and } v=wm2" data-qx-orig-src="https://firebasestorage.googleapis.com/v0/b/quantrexacademy-app.firebasestorage.app/o/questions%2Ffigs%2Fnta_abhyas%2Fjee_main%2Fimages%2F29201_que.png?alt=media" data-qx-storage-src="https://firebasestorage.googleapis.com/v0/b/quantrexacademy-app.firebasestorage.app/o/questions%2Ffigs%2Fnta_abhyas%2Fjee_main%2Fimages%2F29201_que.png?alt=media" style="width: 160px; height: 162px;" />

Options

  1. AEx>Eyandax<ay{E}_{x} > {E}_{y}and{a}_{x} < {a}_{y}
  2. BEx<Eyandax>ay{E}_{x} < {E}_{y}and{a}_{x} > {a}_{y}
  3. CEx>Eyandax>ay{E}_{x} > {E}_{y}and{a}_{x} > {a}_{y}
  4. DEx<Eyandax<ay{E}_{x} < {E}_{y}and{a}_{x} < {a}_{y}

Correct answer

C. Ex>Eyandax>ay{E}_{x} > {E}_{y}and{a}_{x} > {a}_{y}

Step-by-step solution

Rate of cooling (−dTdt)∝\left(- \dfrac{dT}{dt}\right) ∝ emissivity \left(e\right)<br/><br/>Fromthegraph,<br/><br/>(−dTdt)x>(−dTdt)y<br /><br />From the graph,<br /><br />\left(- \dfrac{dT}{dt}\right)x > \left(- \dfrac{dT}{dt}\right)y

∴ex>ey∴{e}_{x} > {e}_{y}

Further emissivity (ee)∝∝ absorptive power (aa) (good absorbers are good emitters also)

∴ax>ay∴{a}_{x} > {a}_{y}
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