The rate of radiation of energy from a hot object is maximum, if its surface is ...........
A
White and smooth
B
Black and rough
C
Black and smooth
D
White and rough
Easy
Download our app for free and get started
B
Black and rough
b (b)
Black and rough surfaces absorb maximum amount of radiation and than radiate the same amount of radiations.
Download our app
and get started for free
Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*
The energy distribution $E$ with the wavelength $(\lambda )$ for the black body radiation at temperature $T\;Kelvin$is shown in the figure. As the temperature is increased the maxima will
Consider two rods of same length and different specific heats $\left(S_{1}, S_{2}\right)$, conductivities $\left(K_{1}, K_{2}\right)$ and area of cross-sections $\left(A_{1}, A_{2}\right)$ and both having temperatures $T_{1}$ and $T_{2}$ at their ends. If rate of loss of heat due to conduction is equal, then
Two metal spheres have radil $r$ and $2 r$ and they emit thermal radiation with maximum intensities at wavelengths $\lambda$ and $2 \lambda$ respectively. The respective ratio of the radiant energy emitted by them per second will be .........
An ice cube of dimensions $60\,cm \times 50\,cm \times 20\,cm$ is placed in an insulation box of wall thickness $1\,cm$. The box keeping the ice cube at $0^{\circ}\,C$ of temperature is brought to a room of temperature $40^{\circ}\,C$. The rate of melting of ice is approximately. (Latent heat of fusion of ice is $3.4 \times 10^{5}\,J\,kg ^{-1}$ and thermal conducting of insulation wall is $0.05\,Wm ^{-10} C ^{-1}$ )
The temperature drop through each layer of a two layer furnace wall is shown in figure. Assume that the external temperature $T_1$ and $T_3$ are maintained constant and $T_1 > T_3$. If the thickness of the layers $x_1$ and $x_2$ are the same, which of the following statements are correct.
Ice starts forming in lake with water at ${0^o}C$ and when the atmospheric temperature is $ - {10^o}C$. If the time taken for $1 \;cm$ of ice be $7$ hours, then the time taken for the thickness of ice to change from $1\; cm$ to $2\; cm$ is
A piece of iron is heated in a flame. It first becomes dull red then becomes reddish yellow and finally turns to white hot. The correct explanation for the above observation is possible by using
The absolute temperatures of two black bodies are $2000 K$ and $3000 K$ respectively. The ratio of wavelengths corresponding to maximum emission of radiation by them will be
In a room where the temperature is ${30^o}C$, a body cools from ${61^o}C$ to ${59^o}C$ in $4$ minutes. The time (in min.) taken by the body to cool from ${51^0}C$ to ${49^0}C$ will be ....... $\min$
A $5cm$ thick ice block is there on the surface of water in a lake. The temperature of air is $-10°C$ ; how much time it will take to double the thickness of the block ...... hour ($L = 80 cal/g, Kicc = 0.004 Erg/s-k, dice = 0.92 g cm^{-3}$)