Wien's Displacement Law, Stefan's Law and Stellar Radii

The radius of stars can be deduced from their luminosity and _____.

The luminosity of a star can be used to calculate stellar radius.

How can the radius of stars can be deduced from their luminosity and temperature ?.

The radius of stars can be deduced from their luminosity.

The sun's angular diameter is measured to be $1920\text{'}\text{'}$. The distance of the sun from the earth is $1.496\times {10}^{11} m$. What is the diameter of the sun?

Measuring the Diameter of the Sun and the Moon

A spherical body of area $A$ and emissivity $e=0.6$ is kept inside a perfectly black body. Energy radiated per second by the body at temperature $T$ is

The wavelength of maximum intensity for emitted radiation from a source is $11\times {10}^{-5} \mathrm{cm}$.  The temperature of this source is $n$ times the temperature of some other source for which the wavelength at maximum intensity is known to be $5.5\times {10}^{-5} \mathrm{cm}$. Find the value of $n$.

A black body is defined as a perfect absorber of radiations. It may or may not be a perfect emitter of radiations.

$\mathrm{A}$ steady current is passing through a cylindrical conductor of radius $r$ placed in vacuum. Assuming Stefan'$\mathrm{s}$ law of radiation, steady temperature will be proportional to

Three very large plates of same area are kept parallel and close to each other. They are considered as ideal black surfaces and have very high thermal conductivity. First and third plates are maintained at absolute temperatures $2 \mathrm{T}$ and $3 \mathrm{T}$ respectively. Temperature of the middle plate in steady state is

A certain perfect black body is such that its temperature is $727{ }^{\mathrm{o}}\mathrm{C}$ and its area is $0.1{\mathrm{m}}^2$. Calculate the heat radiated by the black body in one minute. (Use Stefan's constant $=5.67\times {10}^{-8}$ $\mathrm{W} {\mathrm{m}}^{-2}{\mathrm{s}}^{-1}{\mathrm{k}}^{-4}$)

What is the rate of cooling of two spheres with radii in ratio $1:2$ and densities in the ratio $2:1$ which are of same specific heat, heated to same temperature and left in the same surrounding. 

The peak emission from a black body at a certain temperature occurs at a wavelength of $9000 \stackrel{\circ }{\mathrm{A}}$. On increasing its temperature, the total radiation emitted is increased to $81$ times. At the initial temperature when the peak radiation from the black body is incident on a metal surface, it does not cause any photoemission from the surface. After the increase in temperature, the peak radiation from the black body caused photoemission. To bring these photoelectrons to rest, a potential equivalent to the excitation energy between $n=2$ and $n=3$ Bohr levels of hydrogen atoms is required. Find the work function of the metal (in $\mathrm{e}\mathrm{V}$).

The formula${\lambda }_{m}T = 0.29 \mathrm{cm} \mathrm{K}$is used to obtain the characteristic temperature ranges for different parts of the electromagnetic spectrum. Find the value of temperature(in $\mathrm{K}$) for ${\lambda }_m=5\times {10}^{-5} \mathrm{cm}$.

A black body emits radiations of maximum intensity at $5000 \stackrel{\circ }{\mathrm{A}}$ when its temperature is $1227°\mathrm{C}$. If, its temperature is increased by $1000°\mathrm{C}$  then the maximum intensity of emitted radiation will be at:

The rate of cooling at $600 \mathrm{K}$, if surrounding temperature is $300 \mathrm{K}$ is $H$. The rate of cooling at $900 \mathrm{K}$ is

If the temperature of the Sun were to increase from $T$ to $2T$ and its radius from $R$ to $2R$. The ratio of power radiated by it would become

Two spheres of the same material have radii $1 \mathrm{m}$ and $4 \mathrm{m}$ and temperature $4000 \mathrm{K}$ and $2000 \mathrm{K}$ repectively. The energy radiated per second by the first sphere is

The temperature of a radiating body increases by $30\%$. Then, the increase in the amount of radiation is