If the emissive power of black surface at same
temperature is 400 W/m², the emissive ånd
absorptive powers of the surface assuming it
was initially ordinary surface, are
(Given, Mass of the body m = 4.2 kg,
area of body = 5x10-2 m²,
rate of cooling =;
dt 12
specific heat s = 420 J/kg° C)
(a) e = a = 0.0735 (b) e = a = 0.0435
(c) e = a = 0.0535 (d) e = a = 0.0235
de_ 1 x10-2 °C/min,
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Answered by
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Explanation:
PHYSICS
The spectral emissive power E
λ
for a body at temperature T
1
is plotted against the wavelength and area under the curve is found to be A. At a different temperature T
2
the area`is found to be 9A. Then
λ
2
λ
1
is :
question
December 20, 2019avatar
Sreetama Vadisetti
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ANSWER
The spectral emissive power is directly proportional to the fourth power of the absolute temperature.
E
λ
=kT
4
E
1
=kT
1
4
=A
E
2
=kT
2
4
=9A
E
1
E
2
=(
T
1
T
2
)
4
=9
T
1
T
2
=
3
T
2
=
3
T
1
According to Wien's displacement law:
λT=b=constant
λ
1
T
1
=λ
2
T
2
λ
2
λ
1
=
T
1
T
2
=
3
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