G L Mittal and TARUN MITTAL Solutions for Chapter: Thermal Radiation, Exercise 2: NUMERICALS

The temperature of a silver sphere of radius $5 \mathrm{cm} \mathrm{is} 527°\mathrm{C}$. If the emissivity is $0.04$ find out the energy emitted per sec from the surface of the sphere.

Calculate the rate of emission in $\mathrm{W} {\mathrm{cm}}^{-2}$ by a surface at $227°\mathrm{C}$ if its emissivity is $0.6$.

A metallic blackened sphere of radius of $7 \mathrm{cm}$ and mass $10 \mathrm{kg}$ heated to $227°\mathrm{C}$ and suspended in a box maintained at $27°\mathrm{C}$. Calculate the net rate of heat loss by the sphere. What will be temperature of sphere after $5 \min$? Specific heat of the metal is $420 \mathrm{J} {\mathrm{kg}}^{-1}{\mathrm{K}}^{-1}$.

The sun's surface radiates energy at the rate of $6.3\times {10}^7 \mathrm{W} {\mathrm{m}}^{-2}$. Use Stefan's law to estimate the temperature of sun's surface where Stefan's constant is $\mathrm{\sigma }=5.65\times {10}^{-8} \mathrm{W} {\mathrm{m}}^2 {\mathrm{K}}^{-4}$

Experimentally the intensity of solar radiation is maximum at $4753 \stackrel{\circ }{\mathrm{A}}$ in the visible region. Estimate the temperature of the sun assuming it as a black body. (Wien's constant is $2.92\times {10}^{-3} \mathrm{m} \mathrm{K}$)

Two stars X and Y emits maximum radiation at $4800 \stackrel{\circ }{\mathrm{A}}$ and $6000 \stackrel{\circ }{\mathrm{A}}$. If the temperature of Y is $5800 \mathrm{K}$ then what will be the temperature of X ?

In the energy distribution of the sun's spectrum, the maxima occurs at $4750 \stackrel{\circ }{\mathrm{A}}$ and the sun's temperature is $5777°\mathrm{C}$. What will be the temperature of a star whose maximum spectral energy distribution is at $9500 \stackrel{\circ }{\mathrm{A}}$.

Solar radiation value of ${\mathrm{\lambda }}_{\mathrm{m}}=4753\mathrm{A}°$ and the temperature of the sun is $6083.3 \mathrm{K}$. Calculate the value of Wien's constant.