Taking into account the radiation that a human body emits which of the following statements is true?

1.	The radiation is emitted only during the day.
2.	The radiation is emitted during the summers and absorbed during the winters.
3.	The radiation emitted lies in the ultraviolet region and hence is not visible.
4.	The radiation emitted is in the infra-red region.

According to Wein's law:
1. ${\mathrm{\lambda }}_{\mathrm{m}}\mathrm{T}$= constant                 

2. $\frac{{\mathrm{\lambda }}_{\mathrm{m}}}{\mathrm{T}}$= constant

3. $\frac{T}{{\mathrm{\lambda }}_{\mathrm{m}}}$= constant                 

4. $\mathrm{T}+{\mathrm{\lambda }}_{\mathrm{m}}$= constant

A black body at \(200\) K is found to emit maximum energy at a wavelength of \(14\) \(\mu \)m. When its temperature is raised to \(1000\) K, the wavelength at which maximum energy is emitted will be:

If the temperature of the sun becomes twice its present temperature, then:

A black body has a maximum wavelength at a temperature of 2000 K. Its corresponding wavelength at temperatures of 3000 K will be: 

The temperature of an object is \(400^{\circ}\mathrm{C}\)$\mathrm{}$. The temperature of the surroundings may be assumed to be negligible. What temperature would cause the energy to radiate twice as quickly? (Given, \(2^{\frac{1}{4}} \approx 1.18\))
1. \(200^{\circ}\mathrm{C}\)
2. 200 K
3. \(800^{\circ}\mathrm{C}\)$\mathrm{}$         
4. 800 K

If the temperature of the body is increased from \(-73^{\circ}\mathrm{C}\)$\mathrm{}$ to \(327^{\circ}\mathrm{C}\)$\mathrm{}$, then the ratio of energy emitted per second in both cases is:
1. 1 : 3                         
2. 1 : 81
3. 1 : 27                       
4. 1 : 9

If the sun’s surface radiates heat at $6.3\times {10}^7$ ${\mathrm{Wm}}^{-\mathrm{2 }}$then the temperature of the sun, assuming it to be a black body, will be:
$\left(\mathrm{\sigma }=5.7\times {10}^{-8}\right)$ ${\mathrm{Wm}}^{-2}{\mathrm{K}}^{-4}$
1. $5.8\times {10}^3$ $\mathrm{K}$
2. $8.5\times {10}^3$ $\mathrm{K}$
3. $3.5\times {10}^8$ $\mathrm{K}$
4. $5.3\times {10}^8$ $\mathrm{K}$

Consider two hot bodies, ${\mathrm{B}}_1$ and ${\mathrm{B}}_2$ which have temperatures of \(100^{\circ}\mathrm{C}\)$\mathrm{}$ and \(80^{\circ}\mathrm{C}\)$\mathrm{}$ respectively at t=0. The temperature of the surroundings is \(40^{\circ}\mathrm{C}\)$\mathrm{}$. The ratio of the respective rates of cooling ${\mathrm{R}}_1$ and ${\mathrm{R}}_2$ of these two bodies at t = 0 will be:
1. ${\mathrm{R}}_1:{\mathrm{R}}_2=3:2$
2. ${\mathrm{R}}_1:{\mathrm{R}}_2=5:4$
3. ${\mathrm{R}}_1:{\mathrm{R}}_2=2:3$
4. ${\mathrm{R}}_1:{\mathrm{R}}_2=4:5$

Three rods of identical area of cross-section and made from the same metal form the sides of an isosceles triangle ABC, which is right-angled at B. The points A and B are maintained at temperatures T and $\sqrt{2}\mathrm{T}$ respectively. In the steady state, the temperature of point C is ${\mathrm{T}}_{\mathrm{C}}$. Assuming that only heat conduction takes place, $\frac{{\mathrm{T}}_{\mathrm{C}}}{\mathrm{T}}$ is equal to:
1. $\frac{1}{\left(\sqrt{2}+1\right)}$
2. $\frac{3}{\left(\sqrt{2}+1\right)}$
3. $\frac{1}{2\left(\sqrt{2}-1\right)}$                  
4. $\frac{1}{\sqrt{3}\left(\sqrt{2}-1\right)}$