The temperatures of two bodies A and B are respectively 727$°\mathrm{C}$ and 327$°\mathrm{C}$. The ratio of the rates of heat radiated by them is

(a)727:327                        (b) 5 : 3
(c) 25 : 9                           (d) 625 : 81

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Stefan-Boltzmann law
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Difficulty Level:

The energy emitted per second by a black body at 27$°\mathrm{C}$ is 10 J. If the temperature of the black body is increased to 327$°\mathrm{C}$, the energy emitted per second will be

(a) 20 J              (b) 40 J
(c) 80 J              (d) 160 J

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Stefan-Boltzmann law
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The radiant energy from the sun incident normally at the surface of earth is . What would have been the radiant energy incident normally on the earth, if the sun had a temperature twice of the present one ?

(a)                     (b)
(c)                     (d)

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Stefan-Boltzmann law
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If the temperature of the sun (black body) is doubled, the rate of energy received on earth will be increased by a factor of
(a) 2                         (b) 4
(c) 8                         (d) 16

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Stefan-Boltzmann law
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The ratio of energy of emitted radiation of a black body at 27$°\mathrm{C}$ and 927$°\mathrm{C}$ is
(a) 1 : 4                  (b) 1 : 16
(c) 1 : 64                 (d) 1 : 256

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Stefan-Boltzmann law
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Two spherical black bodies of radii ${\mathrm{r}}_{1}$ and ${\mathrm{r}}_{2}$ and with surface temperature ${\mathrm{T}}_{1}$ and ${\mathrm{T}}_{2}$ respectively radiate the same power. Then the ratio of ${\mathrm{r}}_{1}$ and ${\mathrm{r}}_{2}$ will be

(a) ${\left(\frac{{\mathrm{T}}_{2}}{{\mathrm{T}}_{1}}\right)}^{2}$                (b) ${\left(\frac{{\mathrm{T}}_{2}}{{\mathrm{T}}_{1}}\right)}^{4}$
(c) ${\left(\frac{{\mathrm{T}}_{1}}{{\mathrm{T}}_{2}}\right)}^{2}$                (d) ${\left(\frac{{\mathrm{T}}_{1}}{{\mathrm{T}}_{2}}\right)}^{4}$

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Stefan-Boltzmann law
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A black body is at a temperature 300 K. It emits energy at a rate, which is proportional to

(a) 300             (b) ${\left(300\right)}^{2}$
(c) ${\left(300\right)}^{3}$         (d)  ${\left(300\right)}^{4}$

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Stefan-Boltzmann law
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Two identical metal balls at temperature 200$°\mathrm{C}$ and 400$°\mathrm{C}$ kept in air at 27$°\mathrm{C}$. The ratio of net heat loss by these bodies is
(a) 1/4                  (b) 1/2
(c) 1/16                (d) $\frac{{473}^{4}-{300}^{4}}{{673}^{4}-{300}^{4}}$

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Stefan-Boltzmann law
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A black body radiates 20 W at temperature 227$°\mathrm{C}$. If temperature of the black body is changed to 727$°\mathrm{C}$ then its radiating power will be

(a) 120W                  (b) 240 W
(c) 320 W                 (d) 360 W

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Stefan-Boltzmann law
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The radiation emitted by a star A is 10,000 times that of the sun. If the surface temperatures of the sun and the star A are 6000 K and 2000 K respectively, the ratio of the radii of the star A and the sun is
(a) 300 : 1                     (b) 600 : 1
(c) 900 : 1                     (d) 1200 : 1

Concept Questions :-

Stefan-Boltzmann law