Multiple Choice Questions
1.512 calories of
radiation is incident on a body. It absorbs 220 calories the coefficient of
emission is
a) 0.43
b) 0.57
c) 1.7
d) 0.34
2.Heat energy received by
the earth from the sun is due to
a) Convection
b) Radiation
c) Reflection of light
d) Transmission of light
3.Two sphere of same
material have radii r1 and r2. they are heated to
same temperature and kept
in same enclosure at low temperature their rates of
loss of heat are in the ratio
a)r22/r12
b)r12/r22
c)r1/r2
d)r2/r1
4. Two stars A and B
radiate maximum energy at 3600°A and 3600°A respectively. Then the ratio
of absolute temperatures of A and B
is
a) 256: 81
b) 81: 256
c) 3: 4
d) 4: 3
5.Emissivity of perfectly
black body is
a) 1
b) 2
c) 5
d) 0
6.Absorptive power of perfectly
black body is
a) Zero
b) Infinity
c) One
d) Constant
7. Newton’s law of cooling
is also applicable to
a) Convection losses
b) Natural convection losses
c) Forced convection losses
d) None of the above
8. Which of the following
statement is wrong?
a) Rough
surfaces are better radiators tan smooth surfaces
b) Highly polished mirror surfaces are very
good radiators
c) Black surfaces are better absorbers then
white ones
d) Black surfaces are better radiators then
white ones
9. The best ideal black
body is
a) Lamp of charcoal heated to high temperature
b) Metal coated with a black dye
c) Glass surface coated with coalter
d) Hollow enclosure blackened inside and having
a small hole
10. The earth intercepts
approximately one billionth of the power radiated by the sun. if the
surface temperature of the sun were to drop by a factor of 2, the average radiant
energy incident
on earth per second would reduce by factor of
a) 2
b) 4
c) 8
d) 16
Answer