Thermal Properties of Matter

The plots of intensity against wavelength for three black bodies at temperatures $T_1$, $T_2$ and $T_3$ are as shown. The wavelengths are such that

If the radiant heat absorbed by the body is $75\%$ of the incident heat and if the coefficient of the reflection is $0.15$, then the coefficient of transmission is

The rate of dissipation of the heat by a black body at temperature $T$ is $Q$. The rate of dissipation of heat by ordinary body of the same area at temperature $3T$ and having emissivity $0.25$, will be nearly

The rectangular surface area $(12\ \text{cm}\times6\ \text{cm})$ of the black body, at a temperature $127^\circ\text{C}$, emits heat energy at the rate of Q units per second. If the length and breadth of the surface…

Assume that the temperature of the surface of the sun is $5000$ K and the surface temperature of another virtual star is $2500$ K. The power radiated by a virtual star is $30$ times the power radiated by the sun. The…

Assuming the Sun to be a perfectly spherical black body of radius $R$ and is at a temperature $T\ \text{K}$, then the total radiant power incident on the Earth at a distance $r$ from the sun is (consider $R_o$ is the…

Two spherical stars, A and B emit black body radiation. The radius of star A is $400$ times that of star B and star A emits power $10^4$ times emitted from star B. $\lambda_A$ and $\lambda_B$ are the wavelengths at…

The ratio of emissive power of perfectly black body at $1327\ ^\circ\text{C}$ to that at $527\ ^\circ\text{C}$ is

Three very large plates of same area are kept parallel (in vertical plane) and close to each other. They are considered as ideal black surfaces and have very high thermal conductivity. The first and third plates are…

A spherical blackbody of radius $10\ m$ is maintained at a temperature $T$, radiating power $P$ with a peak emission wavelength $5000\ \AA$. If the body is compressed uniformly such that its radius becomes $R/2$, while…

Three spheres P, Q and R, having radii of 2 m, 3 m and 4 m respectively, are coated with lamp-black on their outer surfaces. The wavelengths corresponding to maximum intensity are 200 nm, 300 nm and 400 nm respectively.…

The thermal conduction rate '$P_{cond}$' of a slab is given by $P_{cond} = \dfrac{kA(T_1 - T_2)}{x}$, where ' $x$ ' is the thickness of the slab and 'A' is the area . The term that represents thermal resistance ' $R_T$'