Multiple Choice Questions
1. The rate of radiation of
black body at 0°C is E watt. The n the
rate of radiation of this black body at 273°C will be
a) 16 E
b) 8 E
c) 4 E
d) E
2. A black body radiates
energy at the rate of E watt m-2 at a temperature of T Kelvin. When
the temperature is
reduced to T/2 Kelvin, the radiant energy will become
a)E/2
b)E/8
c)E/16
d) None of the above
3. Woolen clothes keep the
body warm, because wool
a) Is a bad conductor
b) Increases the temperature of body
c) Decreases the temperature
d) All of these
4. The good absorber of
heat are
a) Non-emitter
b) Poor-emitter
c) Good-emitter
d) Highly polished
5. The maximum energy in
the thermal radiation from a hot source occurs at a wavelength of
11x10-5 cm. according to
Wien’s law, the temperature of the source (on Kelvin scale) will be n
times the
temperature of another source on (Kelvin scale) for which the wavelength at a
maximum energy is 5.5x10-5 cm. The value of n is
a) 2
b) 4
c) 1/2
d) 1
Answer
6. Two sphere of the same
material have radii 1 m and 4 m and temperature 4000 K and 2000 K respectively.
the energy radiated per second by the first sphere is
a) Greater then by the second
b) Less than that by the second
c) Equal in both cases
d) The information is incomplete to draw and
conclusion
7. A surface at temperature
T0 °K receives power P by
radiation from a small sphere at
temperature T >> T0 and at a distance d. if both T and d are
doubled, the power received by
surface will becomes approximately
a) P
b) 2 P
c) 4 P
d) 16 P
8. If temperature of a
black body increases from 7°C to 287°C, then the rate of energy
radiation becomes
a)
b) 16 times
c) 4 times
d) 2 times
9. A bucket full of hot
water is kept in a room and it cools from 75°C to 70°C in t1 minutes
from 70°C to 65°C in t2 minutes
and from 65°C to 60°C in t3 minutes;
then
a) t1 - t2 = t3
b) t1 < t2 < t3
c) t1 > t2 > t3
d) t1 < t2 > t3
10. The velocity with which
thermal radiation travels in vacuum is
a) 3x106 m/s
b) 3x107 m/s
c) 3x108 m/s
d) 3x10-16 m/s
Answer