Blackbody Radiation

If the temperature of the sun were to increase from $T$  to $2T$ and its radius from $R$  to  $2R$ then the ratio of the radiant energy received on earth to what it was previously will be

A black metal foil is warmed by radiation from a small sphere at temperature $T$ and at a distance $d.$ It is found that the power received by the foil is $P$. If both the temperature and the distance are doubled, the power received by the foil will be
 

The radiation energy density per unit wavelength at a temperature $T$  has a maximum at a wavelength ${\lambda }_0$ . At temperature $2 T$, it will have a maximum wavelength

Solar radiation emitted by sun resembles that emitted by a black body at a temperature of $6000 \mathrm{K}$ . Maximum intensity is emitted at a wavelength of about $4800 \stackrel{°}{\mathrm{A}}$. If the sun were to cool down from $6000 \mathrm{K}$  to $3000 \mathrm{K},$, then the peak intensity would occur at a wavelength

The ratio of radiant energies radiated per unit surface area by two bodies is $16: 1,$ the temperature of hotter body is $1000 \mathrm{K},$ then the temperature of colder body will be

The temperature of two bodies $A$ and $B$ are respectively $727°\mathrm{C}$  and $327°\mathrm{C},$ the ratio of the rates of heat radiated $\left(H_{\mathrm{A}}:H_{\mathrm{B}}\right)$ by them, is

The filament of an evacuated light bulb has a length $10 \mathrm{cm}$, diameter $0.2 \mathrm{mm}$ and emissivity $0.2,$ calculate the power it radiates at $2000 \mathrm{K} \left(\sigma =5.67\times {10}^{-8} \mathrm{W} {\mathrm{m}}^{-2} {\mathrm{K}}^{-4}\right)$. 

 At temperature $T$ , the emissive power and absorption power of a body for certain wavelength are $e_{\lambda }$  and $a_{\lambda }$  respectively, then

Lamp black absorbs radiant heat which is near about

Three bodies $A,B$ and $C$ have equal area which are painted red, yellow and black respectively. If they are at the same temperature, then

If the radius of a star is $R$ and it acts as a black body, what would be the temperature of the star, in which the rate of energy production is $Q$?

Assuming the Sun to be a spherical body of radius $R$ at a temperature of $T \mathrm{K}$, evaluate the total radiant power incident of Earth at a distance $r$ from the Sun, where, $r_0$ is radius of earth and $\sigma$ is Stefan's constant.

The plots of intensity versus wavelength for three black bodies at temperatures $T_1,T_2$ and $T_3$ respectively are as shown. Their temperature is such that

The total radiant energy per unit area, normal to the direction of incidence, received at a distance $R$ from the centre of a star of radius $r$, whose outer surface radiates as a black body at a temperature $T \mathrm{K}$ is given by

(where $\sigma$ is Stefan's constant)

A black body at $227°\mathrm{C}$ radiates heat at the rate of $7$ $\mathrm{cal} {\mathrm{cm}}^{-2} {\mathrm{s}}^{-1}$ . At a temperature of $727°\mathrm{C}$, the rate of heat radiated in the same units will be

The emissive power of a black body at $T=300 \mathrm{K}$ is $100 \mathrm{Watt} {\mathrm{m}}^{-2}$. Consider a body $B$ of area $A=10 {\mathrm{m}}^2$ coefficient of reflectivity $r=0.3$ and coefficient of transmission $t=0.5$. Its temperature is $300 \mathrm{K}$ . Then which of the following is incorrect?
 

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

If the temperature of the sun were to increase from $T$  to $2T$  and its radius from $R$  to $2R$  then the ratio of the radiant energy received on earth to what it was previously will be

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

Which of the following is more close to the black body?