Blackbody

Q.

What is a fine spectrum?

Q. Light is an electromagnetic wave.

1. False
2. True

Q. The sun radiates electromagnetic energy at the rate of $3.9\times {10}^{26}W$. Its radius is $6.96\times {10}^{8}m$. If the distance from the sun to the earth is $1.5\times {10}^{11}m$, then the intensity of sunlight on earth's surface will be (in $W/m^2$):

1. $1.38\times {10}^3$
2. $2.76\times {10}^4$
3. $5.52\times {10}^5$
4. None of these

Q.

A solid sphere and a hollow sphere of the same material and size are heated to the same temperature and allowed to cool in the same surroundings. If the temperature difference between the surrounding and each sphere is T, then

1. the hollow sphere will cool at a faster rate for all values of T

2. the solid sphere will cool at a faster rate for all values of T

3. both spheres will cool at the same rate for all values of T

4. both spheres will cool at the same rate only for small values of T.

Q. Light is an electromagnetic wave.

1. False
2. True

Q. Two identical bodies have temperature 277${}^o$C and 67${}^o$C . If the surrounding temperature is 27${}^o$C , the ratio loss of heat of the two bodies during the same interval of time is (approximately)

1. 4 : 1
2. 8 : 1
3. 12 : 1
4. 16 : 1

Q. Intensity of heat radiation emitted by body is believed to be proportional to fourth power of absolute temperature of the body. The proportionality constant also known as Boltzmann's constant may have possible value of :

1. $5.67\times {10}^{-8}watt/K^4$
2. $5.67\times {10}^{-8}watt/m^2{K}^4$
3. $5.67\times {10}^{-8}J/K^4$
4. $5.67\times {10}^{-8}Js/K^4$

Q. (i) Name the radiation which can be detected by (a) a thermopile (b) a solution of silver chloride.

(ii) Name two sources, each of infrared radiations and ultraviolet radiations.

(iii) Name the material of prism required for obtaining the spectrum of (a) ultraviolet light, (b) infrared radiations

Q. The rate of radiation of a black body at 0 ${}^0$C is E watt. Then the rate of radiation of this black body at 273 ${}^0$C will be :

1. 4 E
2. 8 E
3. E
4. 16 E