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Physics II Lab w answers_Part_14

Physics II Lab w answers_Part_14 - Experiment 6 Radiation...

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39 Experiment 6 Radiation from a Black Body: Stefan-Boltzmann Law Apparatus Blackened hemisphere (metal), heating coil, blackened silver disk, thermocouple, power supply, stop clock etc. Objective To determine the Stefan–Boltzmann constant ° by studying the radiation received from a black body radiator. Theory The total radiation from black body is given by Stefan-Boltzmann relation 4 T R σ = (per cm 2 per sec) ………………. (1) where R is the radiant energy per unit area per unit time and T is the absolute temperature of the body. This relation was empirically deduced by Josef Stefan from the experimental results of John Tyndall and was derived by Ludwig Boltzmann from theoretical considerations based on thermodynamics. Consider a black body radiator at temperature T 1 and a metal disc at temperature T 2 as the receiver of the radiation (fig 1.). If R 1 and R 2 be the radiation absorbed and emitted by the receiving metal disc respectively, then the energy gained per second by the disc is (R 1 - R 2 )A ; where A is the area of cross-section of the disc. If
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