An object is at a temperature of ${400^o}C$. At what temperature would it radiate energy twice as fast? The temperature of the surroundings may be assumed to be negligible
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A sphere of ice at $0^o C$ having initial radius $R$ is placed in an environment having ambient temperature $> 0^o C$. The ice melts uniformly, such that shape remains spherical. After a time $‘t’$ the radius of the sphere has reduced to$r$. Assuming the rate of heat absorption is proportional to the surface area of the sphere at any moment, which graph best depicts $r (t)$.
On investigation of light from three different stars $A, B$ and $C$ , it was found that in the spectrum of $A$ the intensity of red colour is maximum, in $B$ the intensity of blue colour is maximum and in $C$ the intensity of yellow colour is maximum. From these observations it can be concluded that
Two rods of same material have same length and area. The heat $\Delta Q$ flows through them for $12\,minutes$ when they are jointed in series. If now both the rods are joined in parallel, then the same amount of heat $\Delta Q$ will flow in ........ $\min$
A black body of surface area $10cm^2$ is heated to $127°C$ and is suspended in a room at temperature $27°C$ . The initial rate of loss of heat from the body at the room temperature will be ...... $W$
The power radiated by a black body is $P$ and it radiates maximum energy at wavelength,$\lambda_0.$ If the temperature of the black body is now changed so that it radiates maximum energy at wavelength $\frac{3}{4}\lambda_0$, the power radiated by it becomes $nP$. The value of $n$ is
Inside a closed furnace held at a temperature of $400\,\, K,$ we have a black body. A hole of area $10\,\, cm^2$ is opened in the furnace so that sunlight starts falling on black body. The intensity of sunlight is $2000\, W/m^2.$ In the steady state
Two identical rods of copper and iron are coated with wax uniformly. When one end of each is kept at temperature of boiling water, the length upto which wax melts are $8.4cm$ and $4.2cm$ respectively. If thermal conductivity of copper is $0.92$ , then thermal conductivity of iron is
Figure shows three different arrangements of materials $1, 2$ and $3$ to form a wall. Thermal conductivities are $k_1 > k_2 > k_3$ . The left side of the wall is $20\,^oC$ higher than the right side. Temperature difference $\Delta T$ across the material $1$ has following relation in three cases
Certain substance emits only the wavelengths ${\lambda _1},\;{\lambda _2},\;{\lambda _3}$ and ${\lambda _4}$ when it is at a high temperature. When this substance is at a colder temperature, it will absorb only the following wavelengths
Three rods of identical area of cross-section and made from the same metal form the sides of an isosceles triangle $ABC$, right angled at $B$. The points $A$ and $B$ are maintained at temperatures $T$ and $\sqrt 2 T$ respectively. In the steady state the temperature of the point C is ${T_C}$. Assuming that only heat conduction takes place, $\frac{{{T_C}}}{T}$ is equal to