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

A black body at a temperature of 227$°\mathrm{C}$ radiates heat energy at the rate of 5 $\mathrm{cal}/{\mathrm{cm}}^2-\sec$. At a temperature of $727°\mathrm{C}$, the rate of heat radiated per unit area in $\mathrm{cal}/{\mathrm{cm}}^2$ will be 
(1) 80                     

(2) 160

(3) 250                   

(4) 500

A body radiates energy 5W at a temperature of 127$°\mathrm{C}$. If the temperature is increased to 927$°\mathrm{C}$, then it radiates energy at the rate of
(a) 410 W                   (b) 81 W 
(c) 405 W                   (d) 200 W

The temperatures of two bodies A and B are respectively 727$°\mathrm{C}$ and 327$°\mathrm{C}$. The ratio of the rates of heat radiated by them is 

(1)727:327                       

(2) 5 : 3

(3) 25 : 9                           

(4) 625 : 81

The radiant energy from the sun incident normally at the surface of earth is $20 \mathrm{kcal}/{\mathrm{m}}^2\min$. What would have been the radiant energy incident normally on the earth, if the sun had a temperature twice of the present one ?

(a) $160 \mathrm{kcal}/{\mathrm{m}}^2\min$                    (b) $40 \mathrm{kcal}/{\mathrm{m}}^2\min$
(c) $320 \mathrm{kcal}/{\mathrm{m}}^2\min$                    (d) $80 \mathrm{kcal}/{\mathrm{m}}^2\min$

A black body radiates energy at the rate of E $\mathrm{W}/{\mathrm{m}}^2$ at a high temperature TK. When the temperature is reduced to $\frac{\mathrm{T}}{2}\mathrm{K}$, the radiant energy will be

(a) $\frac{\mathrm{E}}{16}$                    (b) $\frac{\mathrm{E}}{4}$
(c) $4\mathrm{E}$                     (d) $16 \mathrm{E}$

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: 

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

A piece of blue glass heated to a high temperature and a piece of red glass at room temperature, are taken inside a dimly lit room. Then  -

1. The blue piece will look blue and red will look as usual

2. Red look brighter red and blue look ordinary blue

3. Blue shines like brighter red compared to the red piece

4.  Both the pieces will look equally red.

Certain substance emits only the wavelengths ${\mathrm{\lambda }}_1, {\mathrm{\lambda }}_2, {\mathrm{\lambda }}_3$ and ${\mathrm{\lambda }}_4$ when it is at a high temperature. When this substance is at a colder temperature, it will absorb only the following wavelengths ?
(a) ${\mathrm{\lambda }}_1$                      (b) ${\mathrm{\lambda }}_2$
(c) ${\mathrm{\lambda }}_1$ and ${\mathrm{\lambda }}_2$          (d)  ${\mathrm{\lambda }}_1, {\mathrm{\lambda }}_2, {\mathrm{\lambda }}_3$ and ${\mathrm{\lambda }}_4$