26274.Co-efficient of reflection, coefficient of absorption and coefficient transmission are related as
a + r + 1 = 1
a + r + t = 1
a + r = -t
a ≠ r + 1
26275.A black body is at a temperature of 500K. it emits energy at a rate which is proportional to
500
$(500)^{2}$
$(500)^{3}$
$(500)^{4}$
26277.The wavelength of maximum energy released during an atomic explosion was 2.93 × $10^{-10}$m. The maximum temperature attained must be (Wien’s constant = 2.93 × $10^{-3}$mK)
5.86 × $10^{7}$K
$10^{-13}$ K
$10^{-7}$ K
$10^{7}$ K
26279.A body cools from 50°C to 46°C in 5 minutes and to 40°C in the next 10 minutes. The surrounding temperature is
30°C
28°C
36°C
32°C
26281.The wavelength of maximum energy release during an atomic explosion was 2.93 × 10-10 m. the maximum temperature attained must be (Wein’s constant = 2.93 × 10-3 mK)
5.86 × 107K
10-13 k
10-7 K
107 K
26282.Which of the following will radiate heat to large extent?
Rough surface
Polished surface
Black rough surface
Black polished surface
26283.Which of the following statement is wrong?
Rough surfaces are better radiators tan smooth surfaces
Highly polished mirror surfaces are very good radiators
Black surfaces are better absorbers then white ones
Black surfaces are better radiators then white ones
26284.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
16 E
8 E
4 E
E
26285.Newton’s law of cooling is also applicable to
Convection losses
Natural convection losses
Forced convection losses
None of the above
26286.Woolen clothes keep the body warm, because wool
Is a bad conductor
Increases the temperature of body
Decreases the temperature
All of these
26287.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
Greater then by the second
Less than that by the second
Equal in both cases
The information is incomplete to draw and conclusion
26288.A surface at temperature $T_{0}$ 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
P
2 P
4 P
16 P
26289.If temperature of a black body increases from 7°C to 287°C, then the rate of energy radiation becomes
$\left(\dfrac{287}{7}\right)^4$ times
16 times
4 times
2 times
26290.A bucket full of hot water is kept in a room and it cools from 75°C to 70°C in $t_{1}$ minutes from 70°C to 65°C in $t_{2}$ minutes and from 65°C to 60°C in $t_{3}$ minutes; then
$t_{1}$ – $t_{2}$ = $t_{3}$
$t_{1}$ < $t_{2}$ < $t_{3}$
$t_{1}$ > $t_{2}$ > $t_{3}$
$t_{1}$ < $t_{2}$ > $t_{3}$
26291.A sphere, a cube and a thin circular plate, all made of the same material and having the same mass are initially heated to a temperature of 3000 K, which of these will cool fastest?
Sphere
Cube
Plate
None
26293.Two spheres made of same material have radii in the ratio 2:1. if both the spheres are at same temperature, then what is the ratio of heat radiation energy emitted per second by them?
1: 4
4: 1
3: 4
4: 3