If between wavelength $\mathrm{\lambda }$ and $\mathrm{\lambda }+\mathrm{d\lambda }$, ${\mathrm{e}}_{\mathrm{\lambda }}$ and ${\mathrm{a}}_{\mathrm{\lambda }}$ be the emissive and absorptive powers of a body and ${\mathrm{E}}_{\mathrm{\lambda }}$ be the emissive power of a perfectly black body, then according to Kirchoff's law, which is true ?

1. ${\mathrm{e}}_{\mathrm{\lambda }}$= ${\mathrm{a}}_{\mathrm{\lambda }}$= ${\mathrm{E}}_{\mathrm{\lambda }}$          

2. ${\mathrm{e}}_{\mathrm{\lambda }}$${\mathrm{E}}_{\mathrm{\lambda }}$=${\mathrm{a}}_{\mathrm{\lambda }}$

3. ${\mathrm{e}}_{\mathrm{\lambda }}$= ${\mathrm{a}}_{\mathrm{\lambda }}$${\mathrm{E}}_{\mathrm{\lambda }}$              

4. ${\mathrm{e}}_{\mathrm{\lambda }}$${\mathrm{a}}_{\mathrm{\lambda }}$${\mathrm{E}}_{\mathrm{\lambda }}$ = constant

When p calories of heat is given to a body, it absorbs q calories; then the absorbtion power of body will be ?

1. p/q                         

2. q/p

3. ${\mathrm{p}}^2/{\mathrm{q}}^2$                     

4. ${\mathrm{q}}^2/{\mathrm{p}}^2$

There is a rough black spot on a polished metallic plate. It is heated upto 1400 K approximately and then at once taken in a dark room. Which of the following statements is true ?

1. In comparison with the plate, the spot will shine more

2. In camparison with the plate, the spot will appear more black

3. The spot and the plate will be equally bright

4. The plate and the black spot can not be seen in the dark room

A black body of surface area 10 ${\mathrm{cm}}^2$ 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 

1. 2.99 W               

2. 1.89 W

3. 1.18 W               

4. 0.99 W

Two identical objects A and B are at temperatures ${\mathrm{T}}_{\mathrm{A}}$ and ${\mathrm{T}}_{\mathrm{B}}$ respectively. Both objects are placed in a room with perfectly absorbing walls maintained at temperatures T(${\mathrm{T}}_{\mathrm{A}}$>T>${\mathrm{T}}_{\mathrm{B}}$)The objects A and B attain temperature T eventually which one of the following is correct statement

1. ‘A’ only emits radiations while B only absorbs them until both attain temperature

2. A loses more radiations than it absorbs while B absorbs more radiations that it emits until temperature T is attained

3. Both A and B only absorb radiations until they attain temperature T

4. Both A and B only emit radiations until they attain temperature T

When the body has the same temperature as that of surroundings

1. It does not radiate heat

2. It radiates the same quantity of heat as it absorbs

3. It radiates less quantity of heat as it receives from surroundings

4. It radiates more quantity of heat as it receives heat from surroundings

The temperature of a liquid drops from 365 K to 361 K in 2 minutes. Find the time during which temperature of the liquid drops from 344 K to 342 K . Temperature of room is 293 K

1. 84 sec                       

2. 72 sec

3. 66 sec                       

4. 60 sec

Newton’s law of cooling, holds good only if the temperature difference between the body and the surroundings is

1. Less than 10$°\mathrm{C}$      

2. More than 10$°\mathrm{C}$

3. Less than 100$°\mathrm{C}$     

4. More than 100$°\mathrm{C}$

The temperature of a body falls from \(50^{\circ}\text{C}\)$\mathrm{}$ to \(40^{\circ}\text{C}\)$\mathrm{}$ in \(10\) minutes. If the temperature of the surroundings is \(20^{\circ}\text{C},\)$\mathrm{ t}$hen the temperature of the body after another \(10\) minutes will be:
1. \(36.6^{\circ}\text{C}\)          
2. \(33.3^{\circ}\text{C}\)$\mathrm{}$
3. \(35^{\circ}\text{C}\)             
4. \(30^{\circ}\text{C}\)$\mathrm{}$

A body takes 5 minutes to cool from 90$°\mathrm{C}$ to 60$°\mathrm{C}$. If the temperature of the surroundings is 20$°\mathrm{C}$, the time taken by it to cool from 60$°\mathrm{C}$ to 30$°\mathrm{C}$ will be. 

1. 5 min                   

2. 8 min

3. 11 min                 

4. 12 min