question_answer 1)
The amount of radiation emitted by a perfectly black body is proportional to [AFMC 1995; Pb. PMT 1997; CPMT 1974, 98, 02; AIIMS 2000; DPMT 1995, 98, 02]
A)
Temperature on ideal gas scale done
clear
B)
Fourth root of temperature on ideal gas scale done
clear
C)
Fourth power of temperature on ideal gas scale done
clear
D)
Source of temperature on ideal gas scale done
clear
View Solution play_arrow
question_answer 2)
A metal ball of surface area \[200\ c{{m}^{2}}\] and temperature \[{{527}^{o}}C\] is surrounded by a vessel at \[{{27}^{o}}C\]. If the emissivity of the metal is 0.4, then the rate of loss of heat from the ball is \[(\sigma =5.67\times {{10}^{-8}}J/{{m}^{2}}\ -s-{{k}^{4}})\] [MP PMT/PET 1988]
A)
108 joules approx. done
clear
B)
168 joules approx. done
clear
C)
182 joules approx. done
clear
D)
192 joules approx. done
clear
View Solution play_arrow
question_answer 3)
The rate of radiation of a black body at 0°C is EJ/sec. The rate of radiation of this black body at \[{{273}^{o}}C\] will be [MP PMT 1989; Kerala PET 2002; UPSEAT 2001]
A)
\[16\ E\] done
clear
B)
\[{{T}_{2}}=8{{T}_{1}}\] done
clear
C)
\[4\ E\] done
clear
D)
\[E\] done
clear
View Solution play_arrow
question_answer 4)
A black body radiates energy at the rate of \[E\] W/m2 at a high temperature TK. When the temperature is reduced to \[\frac{T}{2}K\], the radiant energy will be [CPMT 1988; UPSEAT 1998; MNR 1993; SCRA 1996; MP PMT 1992; DPMT 2001; MH CET 2001]
A)
\[\frac{E}{16}\] done
clear
B)
\[\frac{E}{4}\] done
clear
C)
\[4E\] done
clear
D)
\[16E\] done
clear
View Solution play_arrow
question_answer 5)
An object is at a temperature of \[{{400}^{o}}C\]. At what temperature would it radiate energy twice as fast? The temperature of the surroundings may be assumed to be negligible [MP PMT 1990; DPMT 2002]
A)
\[{{200}^{o}}C\] done
clear
B)
\[200\ K\] done
clear
C)
\[{{800}^{o}}C\] done
clear
D)
800 K done
clear
View Solution play_arrow
question_answer 6)
A black body at a temperature of \[{{227}^{o}}C\] radiates heat energy at the rate of 5 cal/cm2-sec. At a temperature of \[{{727}^{o}}C\], the rate of heat radiated per unit area in cal/cm2will be [MP PET 1987; MH CET 2002]
A)
80 done
clear
B)
160 done
clear
C)
250 done
clear
D)
500 done
clear
View Solution play_arrow
question_answer 7)
Energy is being emitted from the surface of a black body at \[{{127}^{o}}C\] temperature at the rate of \[1.0\times {{10}^{6}}J/\sec -{{m}^{2}}\]. Temperature of the black body at which the rate of energy emission is \[16.0\times {{10}^{6}}J/\sec -{{m}^{2}}\] will be [MP PMT 1991; AFMC 1998]
A)
\[{{254}^{o}}C\] done
clear
B)
\[{{508}^{o}}C\] done
clear
C)
\[{{527}^{o}}C\] done
clear
D)
\[{{727}^{o}}C\] done
clear
View Solution play_arrow
question_answer 8)
In MKS system, Stefan's constant is denoted by \[\sigma \]. In CGS system multiplying factor of \[\sigma \]will be
A)
1 done
clear
B)
\[{{10}^{3}}\] done
clear
C)
\[{{10}^{5}}\] done
clear
D)
\[{{10}^{2}}\] done
clear
View Solution play_arrow
question_answer 9)
If temperature of a black body increases from \[{{7}^{o}}C\] to \[{{287}^{o}}C\], then the rate of energy radiation increases by [AIIMS 1997; Haryana PMT 2000; RPMT 2003]
A)
\[{{\left( \frac{287}{7} \right)}^{4}}\] done
clear
B)
16 done
clear
C)
4 done
clear
D)
2 done
clear
View Solution play_arrow
question_answer 10)
The temperature of a piece of iron is \[{{27}^{o}}C\] and it is radiating energy at the rate of \[Q\ kW{{m}^{-2}}\]. If its temperature is raised to \[{{151}^{o}}C\], the rate of radiation of energy will become approximately [MP PET 1992]
A)
\[2Q\ kW{{m}^{-2}}\] done
clear
B)
\[4Q\ kW{{m}^{-2}}\] done
clear
C)
\[6Q\ kW{{m}^{-2}}\] done
clear
D)
\[8Q\ kW{{m}^{-2}}\] done
clear
View Solution play_arrow
question_answer 11)
The temperatures of two bodies A and B are \[{{727}^{o}}C\] and \[{{127}^{o}}C\]. The ratio of rate of emission of radiations will be [MP PET 1986]
A)
727/127 done
clear
B)
625/16 done
clear
C)
1000/400 done
clear
D)
100/16 done
clear
View Solution play_arrow
question_answer 12)
The temperature at which a black body of unit area loses its energy at the rate of 1 joule/second is
A)
\[-{{65}^{o}}C\] done
clear
B)
\[{{65}^{o}}C\] done
clear
C)
65 K done
clear
D)
None of these done
clear
View Solution play_arrow
question_answer 13)
The area of a hole of heat furnace is \[{{10}^{-4}}{{m}^{2}}\]. It radiates \[1.58\times {{10}^{5}}\]calories of heat per hour. If the emissivity of the furnace is 0.80, then its temperature is
A)
1500 K done
clear
B)
2000 K done
clear
C)
2500 K done
clear
D)
3000 K done
clear
View Solution play_arrow
question_answer 14)
Two spheres \[P\] and \[Q\], of same colour having radii \[8\ cm\] and \[2\ cm\] are maintained at temperatures \[{{127}^{o}}C\] and \[{{527}^{o}}C\] respectively. The ratio of energy radiated by \[P\] and \[Q\] is [MP PMT 1994]
A)
0.054 done
clear
B)
0.0034 done
clear
C)
1 done
clear
D)
2 done
clear
View Solution play_arrow
question_answer 15)
A body radiates energy \[5W\] at a temperature of \[{{127}^{o}}C\]. If the temperature is increased to \[{{927}^{o}}C\], then it radiates energy at the rate of [MP PET 1994;BHU 1995; CPMT 1998; AFMC 2000]
A)
\[410W\] done
clear
B)
\[81\ W\] done
clear
C)
\[405\ W\] done
clear
D)
\[200\ W\] done
clear
View Solution play_arrow
question_answer 16)
A thin square steel plate with each side equal to 10 cm is heated by a blacksmith. The rate of radiated energy by the heated plate is 1134 W. The temperature of the hot steel plate is (Stefan's constant \[\sigma =5.67\times {{10}^{-8}}watt\ {{m}^{-2}}{{K}^{-4}}\], emissivity of the plate = 1) [MP PMT 1995]
A)
\[1000\ K\] done
clear
B)
\[1189\ K\] done
clear
C)
\[2000\ K\] done
clear
D)
\[2378\ K\] done
clear
View Solution play_arrow
question_answer 17)
The temperatures of two bodies \[A\] and \[B\] are respectively \[{{727}^{o}}C\] and \[{{327}^{o}}C\]. The ratio \[{{H}_{A}}:{{H}_{B}}\] of the rates of heat radiated by them is [UPSEAT 1999; MP PET 1999; MH CET 2000; AIIMS 2000]
A)
\[727:327\] done
clear
B)
5 : 3 done
clear
C)
25 : 9 done
clear
D)
625 : 81 done
clear
View Solution play_arrow
question_answer 18)
The energy emitted per second by a black body at \[{{27}^{o}}C\] is \[10\ J\]. If the temperature of the black body is increased to \[{{327}^{o}}C\], the energy emitted per second will be [CPMT 1999; DCE 1999]
A)
\[20\ J\] done
clear
B)
\[40\ J\] done
clear
C)
\[80\ J\] done
clear
D)
\[160\ J\] done
clear
View Solution play_arrow
question_answer 19)
The radiant energy from the sun incident normally at the surface of earth is \[20\ kcal/{{m}^{2}}min\]. What would have been the radiant energy incident normally on the earth, if the sun had a temperature twice of the present one [CBSE PMT 1998; Pb. PET 2001]
A)
\[160\ kcal/{{m}^{2}}\ min\] done
clear
B)
\[40\ kcal/{{m}^{2}}\ min\] done
clear
C)
\[320\ kcal/{{m}^{2}}\ min\] done
clear
D)
\[80\ kcal/{{m}^{2}}\ min\] done
clear
View Solution play_arrow
question_answer 20)
A spherical black body with a radius of \[12\ cm\] radiates \[440\ W\] power at \[500\ K\]. If the radius were halved and the temperature doubled, the power radiated in watt would be [IIT 1997 Re-Exam]
A)
225 done
clear
B)
450 done
clear
C)
900 done
clear
D)
1800 done
clear
View Solution play_arrow
question_answer 21)
If the temperature of the sun (black body) is doubled, the rate of energy received on earth will be increased by a factor of [CBSE PMT 1993; BHU 2003; RPMT 2004; CPMT 2004]
A)
2 done
clear
B)
4 done
clear
C)
8 done
clear
D)
16 done
clear
View Solution play_arrow
question_answer 22)
The ratio of energy of emitted radiation of a black body at \[{{27}^{o}}C\] and \[{{927}^{o}}C\] is [Pb. PMT 1995; CPMT 1997, 2000; CBSE PMT 2000; DPMT 1998, 02, 03]
A)
1 : 4 done
clear
B)
1 : 16 done
clear
C)
1 : 64 done
clear
D)
1 : 256 done
clear
View Solution play_arrow
question_answer 23)
If the temperature of a black body be increased from \[{{27}^{o}}C\] to \[{{327}^{o}}C\] the radiation emitted increases by a fraction of [Pb. PET 1997; JIPMER 1999]
A)
16 done
clear
B)
8 done
clear
C)
4 done
clear
D)
2 done
clear
View Solution play_arrow
question_answer 24)
The rectangular surface of area 8 cm \[\times \] 4cm of a black body at a temperature of \[{{127}^{o}}C\] emits energy at the rate of E per second. If the length and breadth of the surface are each reduced to half of the initial value and the temperature is raised to \[{{327}^{o}}C\], the rate of emission of energy will become [MP PET 2000]
A)
\[\frac{3}{8}E\] done
clear
B)
\[\frac{81}{16}E\] done
clear
C)
\[\frac{9}{16}E\] done
clear
D)
\[\frac{81}{64}E\] done
clear
View Solution play_arrow
question_answer 25)
At temperature T, the power radiated by a body is Q watts. At the temperature 3T the power radiated by it will be [MP PET 2000]
A)
3 Q done
clear
B)
9 Q done
clear
C)
27 Q done
clear
D)
81 Q done
clear
View Solution play_arrow
question_answer 26)
Two spherical black bodies of radii \[{{r}_{1}}\] and \[{{r}_{2}}\] and with surface temperature \[{{T}_{1}}\]and \[{{T}_{2}}\] respectively radiate the same power. Then the ratio of \[{{r}_{1}}\] and \[{{r}_{2}}\] will be [KCET 2001; UPSEAT 2001]
A)
\[{{\left( \frac{{{T}_{2}}}{{{T}_{1}}} \right)}^{2}}\] done
clear
B)
\[{{\left( \frac{{{T}_{2}}}{{{T}_{1}}} \right)}^{4}}\] done
clear
C)
\[{{\left( \frac{{{T}_{1}}}{{{T}_{2}}} \right)}^{2}}\] done
clear
D)
\[{{\left( \frac{{{T}_{1}}}{{{T}_{2}}} \right)}^{4}}\] done
clear
View Solution play_arrow
question_answer 27)
Temperature of a black body increases from \[{{327}^{o}}C\,\text{to}\,\text{92}{{\text{7}}^{\text{o}}}C\], the initial energy possessed is 2KJ, what is its final energy [DCE 2001]
A)
32 KJ done
clear
B)
320 KJ done
clear
C)
1200 KJ done
clear
D)
None of these done
clear
View Solution play_arrow
question_answer 28)
The original temperature of a black body is \[{{727}^{o}}C.\]The temperature at which this black body must be raised so as to double the total radiant energy, is [Pb. PMT 2001]
A)
971 K done
clear
B)
1190 K done
clear
C)
2001 K done
clear
D)
1458 K done
clear
View Solution play_arrow
question_answer 29)
Two black metallic spheres of radius 4m, at 2000 K and 1m at 4000 K will have ratio of energy radiation as [RPET 2000; AIEEE 2002]
A)
1 : 1 done
clear
B)
4 : 1 done
clear
C)
1 : 4 done
clear
D)
2 : 1 done
clear
View Solution play_arrow
question_answer 30)
The energy spectrum of a black body exhibits a maximum around a wavelength \[{{\lambda }_{o}}.\] The temperature of the black body is now changed such that the energy is maximum around a wavelength \[\frac{3{{\lambda }_{o}}}{4}\].The power radiated by the black body will now increase by a factor of [KCET 2002]
A)
256/81 done
clear
B)
64/27 done
clear
C)
16/9 done
clear
D)
4/3 done
clear
View Solution play_arrow
question_answer 31)
A black body is at a temperature 300 K. It emits energy at a rate, which is proportional to [Pb. PMT 1998; AIIMS 2002; MH CET 2003]
A)
\[300\] done
clear
B)
\[{{(300)}^{2}}\] done
clear
C)
\[{{(300)}^{3}}\] done
clear
D)
\[{{(300)}^{4}}\] done
clear
View Solution play_arrow
question_answer 32)
If the temperature of a hot body is increased by 50% then the increase in the quantity of emitted heat radiation will be [RPET 1998; EAMCET 2001; MP PMT 2003]
A)
125% done
clear
B)
200% done
clear
C)
300% done
clear
D)
400% done
clear
View Solution play_arrow
question_answer 33)
Two identical metal balls at temperature \[{{200}^{o}}C\]and \[{{400}^{o}}C\] kept in air at \[{{27}^{o}}C\]. The ratio of net heat loss by these bodies is [CPMT 2002]
A)
1/4 done
clear
B)
1/2 done
clear
C)
1/16 done
clear
D)
If temperature of surrounding is considered then net loss of energy of a body by radiation \[Q=A\varepsilon \sigma ({{T}^{4}}-T_{0}^{4})t\]Þ\[Q\propto ({{T}^{4}}-T_{0}^{4})\] Þ \[\frac{{{Q}_{1}}}{{{Q}_{2}}}=\frac{T_{1}^{4}-T_{0}^{4}}{T_{2}^{4}-T_{0}^{4}}\] \[=\frac{{{(273+200)}^{4}}-{{(273+27)}^{4}}}{{{(273+400)}^{4}}-{{(273+27)}^{4}}}\]\[=\frac{{{(473)}^{4}}-{{(300)}^{4}}}{{{(673)}^{4}}-{{(300)}^{4}}}\] done
clear
View Solution play_arrow
question_answer 34)
Two spheres made of same material have radii in the ratio 1: 2 Both are at same temperature. Ratio of heat radiation energy emitted per second by them is [MP PMT 2002; MH CET 2004]
A)
1 : 2 done
clear
B)
1 : 8 done
clear
C)
1 : 4 done
clear
D)
1 : 16 done
clear
View Solution play_arrow
question_answer 35)
A black body at a temperature of 127°C radiates heat at the rate of 1 cal/cm2 ´ sec. At a temperature of 527°C the rate of heat radiation from the body in (cal/cm2 ´ sec) will be [MP PET 2002]
A)
16.0 done
clear
B)
10.45 done
clear
C)
4.0 done
clear
D)
2.0 done
clear
View Solution play_arrow
question_answer 36)
A black body radiates 20 W at temperature \[{{227}^{o}}C\]. If temperature of the black body is changed to \[{{727}^{o}}C\] then its radiating power will be [CBSE PMT 2002; DCE 1999, 03; AIIMS 2003]
A)
120W done
clear
B)
240 W done
clear
C)
320 W done
clear
D)
360 W done
clear
View Solution play_arrow
question_answer 37)
Two spheres of same material have radius 1m and 4 m and temperature 4000K and 2000K respectively. The energy radiated per second by the first sphere is [Pb. PMT 2002]
A)
Greater than that by the second done
clear
B)
Less than that by the second done
clear
C)
Equal in both cases done
clear
D)
The information is incomplete done
clear
View Solution play_arrow
question_answer 38)
The radiation emitted by a star A is 10,000 times that of the sun. If the surface temperatures of the sun and the star A are 6000 K and 2000 K respectively, the ratio of the radii of the star A and the sun is [EAMCET 2003]
A)
300 : 1 done
clear
B)
600 : 1 done
clear
C)
900 : 1 done
clear
D)
1200 : 1 done
clear
View Solution play_arrow
question_answer 39)
A black body radiates at the rate of W watts at a temperature T. If the temperature of the body is reduced to T/3, it will radiate at the rate of (in Watts) [BHU 1998; MP PET 2003]
A)
\[\frac{W}{81}\] done
clear
B)
\[\frac{W}{27}\] done
clear
C)
\[\frac{W}{9}\] done
clear
D)
\[\frac{W}{3}\] done
clear
View Solution play_arrow
question_answer 40)
Star A has radius r surface temperature T while star B has radius 4r and surface temperature T/2. The ratio of the power of two starts, PA : PB is [MP PMT 2004]
A)
16 : 1 done
clear
B)
1 : 16 done
clear
C)
1 : 1 done
clear
D)
1 : 4 done
clear
View Solution play_arrow
question_answer 41)
Suppose the sun expands so that its radius becomes 100 times its present radius and its surface temperature becomes half of its present value. The total energy emitted by it then will increase by a factor of [AIIMS 2004]
A)
104 done
clear
B)
625 done
clear
C)
256 done
clear
D)
16 done
clear
View Solution play_arrow
question_answer 42)
If the temperature of the sun were to be increased from T to 2T and its radius from R to 2R, then the ratio of the radiant energy received on the earth to what it was previously will be [AIEEE 2004]
A)
4 done
clear
B)
16 done
clear
C)
32 done
clear
D)
64 done
clear
View Solution play_arrow
question_answer 43)
At 127o C radiates energy is 2.7 ´ 10-3 J/s. At what temperature radiated energy is 4.32 ´ 10 6 J/s [BCECE 2004]
A)
400 K done
clear
B)
4000 K done
clear
C)
80000 K done
clear
D)
40000 K done
clear
View Solution play_arrow
question_answer 44)
If the initial temperatures of metallic sphere and disc, of the same mass, radius and nature are equal, then the ratio of their rate of cooling in same environment will be [J & K CET 2004]
A)
1 : 4 done
clear
B)
4 : 1 done
clear
C)
1 : 2 done
clear
D)
2 : 1 done
clear
View Solution play_arrow
question_answer 45)
A black body radiates energy at the rate of 1 ´ 105 J / s ´m2 at temperature of 227o C. The temperature to which it must be heated so that it radiates energy at rate of 1 ´ 109J/sm2, is [DPMT 2004]
A)
5000 K done
clear
B)
5000 oC done
clear
C)
500 K done
clear
D)
500 oC done
clear
View Solution play_arrow
question_answer 46)
The temperature of the body is increased from ?73 o C to 327 o C, the ratio of energy emitted per second is : [CPMT 2001; Pb. PET 2001]
A)
1 : 3 done
clear
B)
1 : 81 done
clear
C)
1 : 27 done
clear
D)
1 : 9 done
clear
View Solution play_arrow
question_answer 47)
If the temperature of the body is increased by 10%, the percentage increase in the emitted radiation will be [RPMT 2001, 02]
A)
46% done
clear
B)
40% done
clear
C)
30% done
clear
D)
80% done
clear
View Solution play_arrow
question_answer 48)
If the sun?s surface radiates heat at \[6.3\times {{10}^{7}}W{{m}^{-2}}\]. Calculate the temperature of the sun assuming it to be a black body \[(\sigma =5.7\times {{10}^{-8}}W{{m}^{-2}}{{K}^{-4}})\] [BHU (Med.) 2000]
A)
\[5.8\times {{10}^{3}}K\] done
clear
B)
\[8.5\times {{10}^{3}}K\] done
clear
C)
\[3.5\times {{10}^{8}}K\] done
clear
D)
\[5.3\times {{10}^{8}}K\] done
clear
View Solution play_arrow
question_answer 49)
A sphere at temperature 600K is placed in an environment of temperature is 200K. Its cooling rate is H. If its temperature reduced to 400K then cooling rate in same environment will become [CBSE PMT 1999; BHU 2001]
A)
(3/16)H done
clear
B)
(16/3)H done
clear
C)
(9/27)H done
clear
D)
(1/16)H done
clear
View Solution play_arrow
question_answer 50)
The value of Stefan?s constant is [RPMT 2002]
A)
\[5.67\times {{10}^{-8}}W/{{m}^{2}}\text{-}{{K}^{4}}\] done
clear
B)
\[5.67\times {{10}^{-5}}W/{{m}^{2}}\text{-}{{K}^{4}}\] done
clear
C)
\[5.67\times {{10}^{-11}}W/{{m}^{2}}\text{-}\,{{K}^{4}}\] done
clear
D)
None of these done
clear
View Solution play_arrow
question_answer 51)
Rate of cooling at 600K, if surrounding temperature is 300K is R. The rate of cooling at 900K is [DPMT 2002]
A)
\[\frac{16}{3}R\] done
clear
B)
\[2R\] done
clear
C)
\[3R\] done
clear
D)
\[\frac{2}{3}R\] done
clear
View Solution play_arrow
question_answer 52)
A black body of surface area 10cm2 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 [Pb. PET 1997]
A)
2.99 W done
clear
B)
1.89 W done
clear
C)
1.18 W done
clear
D)
0.99 W done
clear
View Solution play_arrow
question_answer 53)
Two identical objects A and B are at temperatures TA and TB respectively. Both objects are placed in a room with perfectly absorbing walls maintained at temperatures T \[({{T}_{A}}>T>{{T}_{B}}).\] The objects A and B attain temperature T eventually which one of the following is correct statement [CPMT 1997]
A)
?A? only emits radiations while B only absorbs them until both attain temperature done
clear
B)
A loses more radiations than it absorbs while B absorbs more radiations that it emits until temperature T is attained done
clear
C)
Both A and B only absorb radiations until they attain temperature T done
clear
D)
Both A and B only emit radiations until they attain temperature T done
clear
View Solution play_arrow
question_answer 54)
When the body has the same temperature as that of surroundings [UPSEAT 1998; Orissa JEE 2004]
A)
It does not radiate heat done
clear
B)
It radiates the same quantity of heat as it absorbs done
clear
C)
It radiates less quantity of heat as it receives from surroundings done
clear
D)
It radiates more quantity of heat as it receives heat from surroundings done
clear
View Solution play_arrow
question_answer 55)
The ratio of radiant energies radiated per unit surface area by two bodies is 16 : 1, the temperature of hotter body is 1000K, then the temperature of colder body will be [UPSEAT 2001]
A)
250 K done
clear
B)
500 K done
clear
C)
1000 K done
clear
D)
62.5 K done
clear
View Solution play_arrow
question_answer 56)
The spectral energy distribution of star is maximum at twice temperature as that of sun. The total energy radiated by star is [J & K CET 2005]
A)
Twice as that of the sun done
clear
B)
Same as that of the sun done
clear
C)
Sixteen times as that of the sun done
clear
D)
One sixteenth of sun done
clear
View Solution play_arrow