1

### GATE ME 2017 Set 2

The emissive power of a blackbody is $P.$ If its absolute temperature is doubled, the emissive power becomes
A
$2P$
B
$4P$
C
$8P$
D
$16$$P$
2

### GATE ME 2016 Set 2

Consider the radiation heat exchange inside an annulus between two very long concentric cylinders. The radius of the outer cylinder is ${R_0}$ and that of the inner cylinder is ${R_i}$ . The radiation view factor of the outer cylinder onto itself is
A
$1 - \sqrt {{{{R_i}} \over {{R_0}}}}$
B
$\sqrt {1 - {{{R_i}} \over {{R_0}}}}$
C
$1 - {\left( {{{{R_i}} \over {{R_0}}}} \right)^{1/3}}$
D
$1 - {{{R_i}} \over {{R_0}}}$
3

### GATE ME 2012

For an opaque surface, the absorptivity $\left( \alpha \right),$ transmissivity $\left( \tau \right)$ and reflectivity $\left( \rho \right)$ are related by the equation:
A
$\alpha + \rho = \tau$
B
$\rho + \alpha + \tau = 0$
C
$\alpha + \rho = 1$
D
$\alpha + \rho = 0$
4

### GATE ME 2005

The following figure was generated from experimental data relating spectral black body emissive power to wave length at three temperatures ${T_1},{T_2}$ and ${T_3}\left( {{T_1} > {T_2} > {T_3}} \right).$ The conclusion is that the measurements are

A
correct because the maximum in ${E_{b\lambda }}$ show the correct trend
B
correct because Planck's law is satisfied
C
wrong because the Stephen Boltzmannn law is not satisfied
D
wrong because Wien's displacement law is not satisfied

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