One likes to sit in the sunshine in the winter season, because:

1.	the air around the body is hot, and the body absorbs heat from it.
2.	we get energy from the sun.
3.	we get heat by conduction from the sun.
4.	none of the above

 

Air is a bad conductor of heat or partly conducts heat. Still, a vacuum is to be placed between the walls of the thermos flask because:

While measuring the thermal conductivity of a liquid, we keep the upper part hot and the lower part cool, so that:

On a clear sunny day, an object at temperature \(T\) is placed on the top of a high mountain. An identical object at the same temperature is placed at the foot of the mountain. If both the objects are exposed to sun-rays for two hours in an identical manner, the object placed on the top of a mountain will register a temperature:

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

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 maintained at \(200~\text{K}\) emits maximum radiation at a wavelength of \(14~\mu \text{m}.\) If its temperature is increased to \(1000~\text{K},\) at what wavelength will the maximum radiation now be emitted?
1. \(14~\mu\text{m}\)
2. \(70~\mu\text{m}\)
3. \(2.8~\mu\text{m}\)
4. \(2.8~\text{nm}\)

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

A black body has a maximum wavelength at a temperature of \(2000~\text K.\) Its corresponding wavelength at temperatures of \(3000~\text K\) 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