a (a)The velocity of heat radiation in vacuum is equal to that of light.
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A black body at a temperature of $1640\,\,K$ has the wavelength corresponding to maximum emission equal to $1.75 \,\,\mu m.$ Assuming the moon to be a perfectly black body, the temperature of the moon, if the wavelength corresponding to maximum emission is $14.35\,\,\mu m$ is.......$K$
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 ........
Three stars $A, B, C$ have surface temperatures $T _{A} ,T _{B}, T _{C}$ respectively. Star $A$ appears bluish, star $B$ appears reddish and star $C$ yellowish. Hence,
$Assertion :$ Bodies radiate heat at all temperature.
$Reason :$ Rate of radiation of heat is proportional to the fourth power of absolute temperature.
Three rods of the same dimension have thermal conductivities $3K$ , $2K$ and $K$ . They are arranged as shown in fig. Given below, with their ends at $100^oC, 50^oC $and $20^oC$. The temperature of their junction is ......... $^oC$
A solid cylinder of length $L$ and radius $r$ is heat upto same temperature as that of a cube of edge length $a$. If both have same material, volume and allowed to cool under similar conditions, then ratio of amount of radiations radiated will be (Neglect radiation emitted from flat surfaces of the cylinder)
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 junction is......... $^oC$