GATE MT 2020 Q3. Select the correct spectra (shown on a log-log scale on the figures) for emission from a gray surface and a black body, both maintained at 1000 K.
GATE MT 2020 Q3. Select the correct spectra (shown on a log-log scale on the figures) for emission from a gray surface and a black body, both maintained at 1000 K.
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As the emissivity of black body is equal to one and gray body emissivity is less than one so the emissive power of black body is higher than that of gray body
As the emissivity of black body is equal to one and gray body emissivity is less than one so the emissive power of black body is higher than that of gray body
See lessBlack body absorbs 100% of the radiations and hence its emmisivity is 1. Grey body absorbs the waves partially and hence its emmisivity is less than 1. So emmisive power of blackbody is greater than grey body
Black body absorbs 100% of the radiations and hence its emmisivity is 1. Grey body absorbs the waves partially and hence its emmisivity is less than 1. So emmisive power of blackbody is greater than grey body
See lessAs per Kirchoff's law: Since no body is perfect emitter, its emittance is less than that of the black body M(b). Thus, emissivity of real (gray M(g)) body is defined by E(g)= M(g)/M(b) Black body : E=1 white body E=0 Gray body: E<1 Selective radiator E'<1 Correct answer is option D.
As per Kirchoff’s law:
Since no body is perfect emitter, its emittance is less than that of the black body M(b). Thus, emissivity of real (gray M(g)) body is defined by E(g)= M(g)/M(b)
Black body : E=1
white body E=0
Gray body: E<1
Selective radiator E'<1
Correct answer is option D.
See lessOption D
Option D
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