A cup of tea cools from ${80^0}C$ to ${60^o}C$ in one minute. The ambient temperature is ${30^o}C$. In cooling from ${60^o}C$ to ${50^o}C$ it will take ....... $\sec$
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A very thin metallic shell of radius $r$ is heated to temperature $T$ and then allowed to cool. The rate of cooling of shell is proportional to ........
A small object is placed at the center of a large evacuated hollow spherical container. Assume that the container is maintained at $0 K$. At time $t =0$, the temperature of the object is $200 K$. The temperature of the object becomes $100 K$ at $t = t _1$ and $50 K$ at $t = t _2$. Assume the object and the container to be ideal black bodies. The heat capacity of the object does not depend on temperature. The ratio $\left( t _2 / t _1\right)$ is. . . . .
The wavelength of maximum intensity of radiation emitted by a star is $289.8 \,nm$. The radiation intensity for the star is : (Stefan’s constant $5.67 \times {10^{ - 8}}W{m^{ - 2}}{K^{ - 4}}$, constant $b = 2898\mu mK)$
The plots of intensity versus wavelength for three black bodies at temperatures $T_1, T_2$ and $T_3$ respectively are as shown. Their temperature are such that
For a black body at temperature $727^{\circ} C$, its radiating power is $60\; watt$ and temperature of surrounding is $227^{\circ} C$. If temperature of black body is changed to $1227^{\circ} C$ then its radiating power will be ..... $watt$
If wavelengths of maximum intensity of radiations emitted by the sun and the moon are $0.5 \times {10^{ - 6}}m$ and ${10^{ - 4}}m$ respectively, the ratio of their temperatures is
The wavelength of maximum intensity of radiation emitted by a star is $289.8 \,nm$. The radiation intensity for the star is : (Stefan’s constant $5.67 \times {10^{ - 8}}W{m^{ - 2}}{K^{ - 4}}$, constant $b = 2898\mu mK)$