A black body at a temperature of $1640 K$ has the wavelength corresponding to maximum emission equal to $1.75$ $\mu $. Assuming the moon to be a perfectly black body, the temperature of the moon, if the wavelength corresponding to maximum emission is $ 14.35$ $\mu $ is ...... $K$
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There are two spherical balls $A$ and $B$ of the same material with same surface, but the diameter of $A$ is half that of $B$. If $A$ and $B$ are heated to the same temperature and then allowed to cool, then
$Assertion :$ A body that is good radiator is also a good absorber of radiation at a given wavelength.
$Reason :$ According to Kirchhoff’s law the absorptivity of a body is equal to its emissivity at a given wavelength.
At a certain temperature for given wave length, the ratio of emissive power of a body to emissive power of black body in same circumstances is known as
Three rods made of the same material and having same cross-sectional area but different lengths $10\,\,cm$, $\,\,20 cm$ and $30\,\,cm$ are joined as shown. The temperature of the joint is ....... $^oC$
A hollow sphere of inner radius $R$ and outer radius $2R$ is made of a material of thermal conductivity $K$. It is surrounded by another hollow sphere of inner radius $2R$ and outer radius $3R$ made of same material of thermal conductivity $K$. The inside of smaller sphere is maintained at $0^o C$ and the outside of bigger sphere at $100^o C$. The system is in steady state. The temperature of the interface will be ........ $^oC$
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