Heat & Thermodynamics - Quanta: BS/MSc Physics Books

1: The temperature of a gas is increased from 27 to 127. The ratio of its mean kinetic energies will be

a. $\frac{10}{9}$
b. $\frac{9}{16}$
c. $\frac{4}{3}$
d. $\frac{\mathbf{3}}{\mathbf{4}}$

2: The internal energy of 1 mole of an ideal gas depends on

a. Only Volume
b. Only Temperature
c. Only pressure
d. Both b and c

3: The mean kinetic energy of a gas molecule at 27 is 6.21 X 10^-21Joule. Its value at 227 will be

a. $12.35\times{10}^{-21}$
b. $11.35\times{10}^{-21}$
c. $\mathbf{10}.\mathbf{35}\times\ {\mathbf{10}}^{-\mathbf{21}}$
d. $9.35\times{10}^{-21}$

4: The value of gamma of triatomic gas (linear arrangement) molecule is

a. $\frac{5}{3}$
b. $\frac{7}{5}$
c. $\frac{8}{6}$
d. $\frac{\mathbf{9}}{\mathbf{7}}$

5: The correct relation between v_rms v_av and v_mp is

a. $v_{rms}\ >\ v_{mp}\ >\ v_{av}$

b. $v_{rms}\ <\ v_{mp}\ <\ v_{av}$

c. $\mathbf{v_{rms}\ >\ v_{av}\ >\ v_{mp}}$

d. $v_{rms}\ <\ v_{av}\ >\ v_{mp}$

6: One mole of a monoatomic gas is mixed with one Mole of a diatomic gas. The molar specific heat of mixture at constant volume will be

a. $\frac{R}{2}$
b. $\R$
c. $\frac{\mathbf{2}}{\mathbit{R}}$
d. $\frac{3}{R}$

7: The value of C_v for 1 mole of polyatomic gas is (f=number of degrees of freedom)

a. $\frac{fR}{2T}$
b. $\frac{\mathbit{fR}}{\mathbf{2}}$
c. $\frac{fRT}{2}$
d. 2fRT

8: The pressure of a gas in a container is ${10}^{-11} Pascal at 27\deg c$ . The number of molecules per unit volume of vessel will be

a. $6\times{10}^{23}cm^{-3}$
b. $2.68\times\ {10}^{19}cm^{-3}$
c. $2.5\times{10}^6cm^{-3}$
d. $\mathbf{2400}\mathbit{c}\mathbit{m}^{-\mathbf{3}}$

9: The value of Gamma for gas X is 1.66 then X is

a. $\mathbf{Ne}$
b. $O_3$
c. $N_2$
d. $H_2$

10: At what temperature will the mean molecular energy of a perfect ga will be one-third of its value at $27\deg c$

a. $10\deg c$
b. ${10}^1K$
c. ${\mathbf{10}}^\mathbf{2}\mathbit{K}$
d. ${10}^3K$

11: In the gas equation PV=RT, V is the volume of

a. 1 mole of gas
b. 1 g of gas
c. gas
d. 1 liter of gas

12: The mean kinetic energy of gas molecules is zero at

a. $10\deg c$
b. $-\mathbf{273}\deg c$
c. 100K
d. $100\deg c$

13: The temperature at which the rms speed of gas molecules becomes double its value at 0\degc is

a. $\mathbf{819}\deg c$
b. $\ 760\deg c$
c. $273\deg c$
d. $224\deg c$

14: The internal energy of a monoatomic ideal gas is

a. only kinetic
b. only potential
c. partially both
d. none

15: If the number of gas molecules in a cubical vessel is increased from N to 3N, then its pressure and total energy will become

a. four times
b. three times
c. double
d. half

16: The temperature below which a gas can be liquefied by increasing its pressure is known as

a. zero
b. neutral temperature
c. critical temperature
d. Boyle temperature

17: The expression for mean free path is

a. $\mathbf{\lambda\ \ =\frac{kT}{\sqrt2{\pi d}^2p}}$
b. $\lambda\ =\frac{\pi dP}{kT}$
c. $\lambda\ =\frac{\pi d^2P}{kT}$
d. $\lambda\ =\frac{kT}{\pi dP}$

18: If the absolute temperature of a gas is tripled, then the rms velocity of gas molecules will become

a. $\frac{1}{3}$
b. $\mathbf{\sqrt3times}$
c. $3\ times$
d. $9\ times$

19: The correct expression for pressure exerted by a gas on wall of a container is

a. $P=\frac{mn}{3l^3}\sqrt{c^3}$
b. $\mathbf{P=\frac{mnc^2}{3l^3}}$
c. $P=\frac{3l^2c^2}{mn}$
d. $P=\frac{mc^2}{3l^2}$

20: If the pressure of a gas is increased then it’s mean free part becomes

a. zero
b. less
c. more
d. ∞

21: If the critical temperature of a gas is 100k then it’s boyle temperature will be

a. $33.3\ K$
b. $103\ K$
c. $\mathbf{337}\ \mathbit{K}$
d. $500\ K$

22: The critical temperature for CO_2 is

a. $31\ K$
b. $31.1\ K$
c. $\mathbf{31}:\mathbf{1}\degc$
d. $31.3\ F$

23: Which of the following expression is not correct for rms velocity

a. $\mathbf{\sqrt{\frac{3\rho}{P}}}$
b. $\sqrt{\frac{3RT}{M}}$
c. $\sqrt{\frac{3PV}{M}}$
d. $\sqrt{\frac{2E_k}{M}}$

24: How many times is the forbidden volume (b). as compared to actul volume of gas molecules

a. double
b. 3 times
c. 4 times
d. 8 times

25: At what temperature the kinetic energy of gas molecules will be doubled of its value at 27\deg c

a. $54\degc$
b. $108\degc$
c. $300\degc$
d. $\mathbf{327}\degc$

26: On which of the following the kinetic theory of gases is not applicable

a. on free electron gas
b. on bound electron
c. on water vapour
d. on smoke particle

27: The mean molecular energy of a gas at 300K will be

a. $2.6\times\ 0^{20}joule$
b. $\mathbf{6}.\mathbf{2}\times\ \mathbf{0}^{-\mathbf{21}}\mathbit{joule}$
c. $6.2\times\ 0-^{20}joule$
d. $6.2\times\ 0^{20}joule$

28: The velocities of three molecules A, B and C of a gas are 1, $\sqrt3$ and $\sqrt5 ms^{-1}$ the value of their rms velocity will be

a. $\mathbf{1}.\mathbf{73}\mathbit{m}\mathbit{s}^{-\mathbf{1}}$
b. $2ms^{-1}$
c. $4ms^{-1}$
d. $9ms^{-1}$

29: If the mean kinetic energy per unit volume of a gas is n times its pressure, then the value of n is

a. 4.5
b. 3.5
c. 2.5
d. 1.5

30: The volume of 0.1 mole of gas at NTP is

a. 0.22 liter
b. 0.24 liter
c. 1 liter
d. 22.4 liter

31: Heat required to melt 1 gram of ice is 80 cal. A man melts 60 gram of ice by chewing in one minute. His power is

a. 1.33 W
b. 0.75 W
c. 336 W
d. 4800 W

32: Taking the unit of work as Joule and the unit of amount of heat aa K cal, the magnitude of joule’s mechanical equilence of heat is

a. 1
b. $4.2\times\ {10}^7$
c. 4.2
d. $\mathbf{4.3\times\ {10}^3}$

33: If 10 grams of ice at -10\degc is added to 40 g of water at 15\degc, the temperature of the mixture is

a. $3.75\degc$
b. $\mathbf{0}\degc$
c. $3\degc$
d. $-2\degc$

34: 10 g of steam passes over an ice block. What amount of ice will melt

a. 8 g
b. 18 g
c. 45 g
d. 80 g

35: The triple point of water is

a. $273\ K$
b. $0\ K$
c. $\mathbf{273}.\mathbf{16}\ \mathbit{K}$
d. $0\degc$

36: Compared to a burn due to water at $100\degc$ , a burn due to steam at $100\degc$ is

a. more dangerous
b. less dangerous
c. equally dangerous
d. none of these

37: According to Boltzmann’s law of equipartition of energy, the energy per degree of freedom and at a temperature TK is

a. $(\frac{3}{2})\ KT$
b. $(\frac{2}{3})\ KT$
c. KT
d. $(\frac{\mathbf{1}}{\mathbf{2}})\ \mathbit{KT}$

38: What is a number of degrees of freedom of an ideal diatomic molecule at ordinary temperature

a. 7
b. 6
c. 5
d. 3

39: To raise the temperature of 100 g of ice at 0\degc\ to\ 10\degc by a heater of 420\ W the time required is

a. 90 min
b. 90 sec
c. 21.2 min
d. 21.2 sec

40: A man is climbing up a spiral type staircase. His degrees of freedom are

a. 1
b. 2
c. 3
d. more than 3

41: The law of equipartition of energy was given by

a. Clausius
b. Maxwell
c. Boltzmann
d. Carnot

42: The law of equipartition of energy is applicable to the system whose constituents are

a. in random motion
b. in orderly motion
c. at rest
d. moving with constant speed

43: The dimension of universal gas constant R are

a. $M^2L^2T^{-2}$
b. $\mathbit{M}\mathbit{L}^\mathbf{2}\mathbit{T}^{-\mathbf{2}}\mathbit{\theta}^{-\mathbf{1}}$
c. $M^2L^2T^{-2}\theta^{-1}$
d. $MLT^{-2}\theta^{-1}$

44: The rms velocity of air at NTP will be……. if density of air is 1.29\ kg/m^3

a. $0.485ms^{-1}$
b. $0.485\times\ {10}^2ms^{-1}$
c. $\mathbf{4}.\mathbf{85}\times\ {\mathbf{10}}^\mathbf{2}\mathbit{m}\mathbit{s}^{-\mathbf{1}}$
d. ${10}^4ms^{-1}$

45: This specific heat of………. is negative

a. $CO_2$
b. Ne
c. saturated vapours
d. none

46: The diameter of oxygen molecules is 2.94\times{10}^{-10}m. The van der Waals gas constant in m^3/mol will be

a. 3.2
b. 32
c. $\ \mathbf{32}\times\ {\mathbf{10}}^{-\mathbf{6}}$
d. 32\times{10}^{-3}

47: The correct relation connecting the universal gas constant R, Avogadro’s number N_A and Boltzmann’s constant K is

a. $R\ =\ NK^2$
b. $K\ =\ NR$
c. $N\ =\ RK$
d. $\mathbf{R\ =\ NK}$

48: The most probable velocity for monotonic gas is

a. $\sqrt{\frac{3KT}{m}}$
b. $\sqrt{\frac{8KT}{\pi m}}$
c. $\mathbf{\sqrt{\frac{2KT}{m}}}$
d. zero

49: This specific heat at constant volume of mixture of $N_2$ and He $(N_2\∶\ He\∶:\ 3\∶\ 2)$ will be

a. $1.7\ R$
b. $\ 1.5\ R$
c. $\ 1.9\ R$
d. $\mathbf{2}.\mathbf{1}\ \mathbit{R}$

50: The behavior of the gases, which can be easily liquefied, is like that of the

a. triatomic gases
b. ideal gases
c. van der Waals gases
d. all of the above

51: The direction of flow of heat between two bodies is determined by

a. internal energy
b. kinetic energy
c. total energy
d. none of these

52: A bottle is inverted and dipped in to a tank. at the bottom of the tank, 3/5th part of the bottle is filled with water. The depth of the tank is

a. 20m
b. 15m
c. 10m
d. 5m

53: Equal mass of helium and oxygen are filled in identical containers. The ratio of pressure exerted by them will be

a. 1:8
b. 1:16
c. 8:1
d. 16:11

54: The mass of 0.5 liter of hydrogen gas at NTP will be approximately

a. 0.0892g
b. 0.045g
c. 2g
d. 22.4g

55: The rms speed of smoke particles of mass 500\times{10}^{-19} at NTP will be

a. $\mathbf{15}\times\ {\mathbf{10}}^{-\mathbf{3}}\mathbit{m}\mathbit{s}^{-\mathbf{1}}$
b. $11.5\times\ {10}^{-3}ms^{-1}$
c. $1.5\times\ {10}^{-3}ms^{-1}$
d. $0.15cms^{-1}$

56: At what temperature will hydrogen molecules escape from earth surface

a. ${10}^1K$
b. ${10}^2K$
c. ${10}^3K$
d. ${\mathbf{10}}^\mathbf{4}\mathbit{K}$

57: The total kinetic energy of 8 liters of helium molecules at 5 atmospheric pressure will be

a. 6078 erg
b. 6078 joule
c. 607 erg
d. 607 joule

58: The amount of work done by the gas system in increasing the volume of 10 moles of an ideal gas from one liter to 20 liter at 0\degc will be

a. zero
b. 3.49\ joule
c. $3.49\times\ {10}^4joule$
d. $\mathbf{6}.\mathbf{79}\times\ {\mathbf{10}}^\mathbf{4}\mathbit{joule}$

59: The minimum number of thermodynamic parameters required to specify the state of gas system is

a. 1
b. 2
c. 3
d. $\infty$

60: The internal energy of a compressed real gas, as compared to that of the normal gas at the same temperature, is

a. less
b. more
c. may less or more
d. none of these

61: The specific heat of a gas at constant pressure as compared to that at constant volume is

a. less
b. equal
c. more
d. constant

62: The ratio of the slopes of adiabatic and isothermal curves is

a. $\gamma^{-2}$
b. $\frac{1}{\gamma}$
c. $\gamma^3$
d. γ

63: The change in internal energy of two moles of a gas during adiabatic expansion is found to be -100 joule. The work done during the process is

a. -100 joule
b. 0
c. 100 joule
d. 200 joule

64: A liquid boils at such a temperature at which the saturated vapour pressure, as compared to atmospheric pressure, is

a. one-third
b. equal
c. half
d. double

65: The heat capacity of a material depends upon

a. density of matter
b. specific heat of matter
c. temperature of matter
d. structure of matter

66: Two samples of a gas A and B, initially at same temperature and pressure are compressed to half their initial volume, A isothermally and B adiabatically. The final pressure in the two cases is related as

a. A=B
b. A>B
c. A<B
d. $A^2=B$

67 A piece of ice at 0\degc is dropped into water at $0\degc$ . Then ice will

a. melt
b. converted to water
c. not melts
d. partially melts

68: In the gas equation $PV=RT,\ V$ represents the volume of

a. 1 mole of gas
b. 1 g of gas
c. 1 liter of gas
d. any mass of gas

69: If in defining the specific heat, temperature is represented in F instead of C then the value of specific heat will

a. converted to heat capacity
b. remain unchanged
c. decrease
d. increase

70: The specific heat of an ideal gas varies as

a. $T^3$
b. $T^2$
c. $T^1$
d. T⁰

71: When an ideal diatomic gas is heated at constant pressure then what fraction of heat given is used to increase internal energy of gas

a. $\frac{2}{5}$
b. $\frac{3}{5}$
c. $\frac{3}{7}$
d. $\frac{\mathbf{5}}{\mathbf{7}}$

72: The pressure and volume of a gas are P and V respectively. If it is compressed suddenly to $\frac{1}{32}$ of its initial volume then it’s final pressure will be

a. $\frac{p}{128}$
b. $\frac{p}{32}$
c. $\mathbf{128}\mathbit{p}$
d. 32p

73: The concept of temperature is related to

a. zeroth law of thermodynamics
b. first law of thermodynamics
c. second law of thermodynamics
d. third law of thermodynamics

74: When a liquid is heated, retaining its liquid state, then its molecules gain

a. kinetic energy
b. potential energy
c. heat energy
d. both kinetic and potential energy

75: The relation between P and T for monotonic gas during adiabatic process is P ∝ T^c the value of c is

a. $\frac{3}{5}$
b. $\frac{2}{5}$
c. $\frac{5}{3}$
d. $\frac{\mathbf{5}}{\mathbf{2}}$

76: The thermodynamic scale of temperature was given by

a. Dewar
b. Fahrenheit
c. Kelvin
d. Carnot

77: If the volume of a gas is decreased by 10% during isothermal process, then its pressure will

a. decreased by 10%
b. increased by 10%
c. decreased by 11.11%
d. increased by 11.11%

78: At the boiling of water the saturated vapour pressure will be (in mm of Hg)

a. 750
b. 760
c. 850
d. 860

79: The ratio of the latent heat of steam to latent heat of ice is

a. $\frac{4}{9}$
b. $\frac{9}{4}$
c. $\frac{4}{27}$
d. $\frac{\mathbf{27}}{\mathbf{4}}$

80: If the temperature of the sink is absolute zero, the efficiency of the heat engine should be

a. 100%
b. 50%
c. zero
d. none of these

81: When the temperature difference between the source and the sink increases, the efficiency of the heat engine will

a. increased
b. decreased
c. not affected
d. may increase or decrease

82: A Carnot engine can be 100% efficient if its sink is at

a. $\mathbf{0}\mathbit{K}$
b. $0\degc$
c. $0\degf$
d. 273K

83: Which of the following is the best container for gas during adiabatic aprocess

a. wood vessel
b. thermos flask
c. copper vessel
d. glass vessel

84: In which of the following process the system always returns to the original thermodynamic state

a. isobaric
b. cyclic
c. isothermal
d. adiabatic

85: What is the value of $\frac{dp}{p}$ for adiabatic expansion of the gas

a. $\frac{\gamma dv}{v}$
b. $-\frac{dv}{v}$
c. $\frac{dv}{v}$
d. $-\frac{\mathbit{\gamma dv}}{\mathbit{v}}$

86: Which of the following has higher efficiency an engine working between the temperatures

a. 40K and 20K
b. 60K and 40K
c. 80K and 60K
d. 100K and 80K

87: Work done during isothermal expansion depends on change in

a. volume
b. pressure
c. both a and b
d. none of these

88: The change in which of the following solely determines the work done by a gas during adiabatic process

a. temperature
b. pressure
c. volume
d. none of these

89: How many dead centers are there in one cycle of steam engine

a. 4
b. 3
c. 2
d. 1

90: For adiabatic expansion of a mono-atomic perfect gas, the volume increases by 2.4%. What is the percentage decrease in pressure

a. 2.4%
b. 4.0%
c. 4.8%
d. 7.1%

91: In free expansion of a gas the internal energy of the system

a. increases
b. decreases
c. unchanged
d. changes

92: If the value of $R\ =\frac{2}{5}\ C_v$ for a gas, then the atomicity of the gas will be

a. monoatomic
b. diatomic
c. polyatomic
d. any of these

93: The value of $\frac{C_p\ }{C_v}$ for the mixture of 2 moles of oxygen and 5 moles of ozone is

a. 1.34
b. 1.41
c. 1.51
d. 1.67

94: For which process the relation dQ=dU is true

a. isobaric
b. isochoric
c. isothermal
d. adiabatic

95: The molar specific heat of an ideal gas at constant pressure and volume are $C_p$ and $C_v$ respectively. The value of $C_v$ is

a. R
b. $\gamma R$
c. $\frac{\mathbit{R}}{\mathbit{\gamma}-\mathbf{1}}$
d. $\frac{\gamma R}{\gamma-1}$

96: Heating of a wheel on applying brakes is due to the relation

a. $p\propto\frac{1}{v}$
b. $p\propto\ T$
c. $\mathbit{W}\propto\ \mathbit{Q}$
d. $v\propto\ T$

97: Out of the following whose specific heat is maximum

a. lead
b. brass
c. glass
d. iron

98: The correct value of temperature on kelvin scale corresponding to 0\degc is

a. 0K
b. $\mathbf{273}.\mathbf{15}\mathbit{K}$
c. 273.2K
d. 273K

99: For the Boyle’s law to hold good, the necessary condition is

a. isothermal
b. adiabatic
c. isobaric
d. isochoric

100: The mechanical equivalent of heat (J) is a

a. conversion factor
b. constant
c. physical quantity
d. none of these

101: The internal energy of an isolated system

a. keeps on changing
b. remains constant
c. zero
d. none of these

102: The number of specific heats for a gas system is

a. 1
b. 2
c. 3
d. \infty

103: The internal energy of a piece of lead when beaten by a hammer will

a. increase
b. decrease
c. remains constant
d. may increase and decrease

104: Two steam engine A and B have their sources respectively at 700k and 650k and their sink at 350k and 300k. Then

a. A is more efficient than B
b. B is more efficient than A
c. Both are equally efficient
d. depends on fuel used in A and B

105: The temperature, which is the same in C and F, is

a. -20
b. 20
c. -40
d. 40

106: Isobaric bulk modulus of elasticity is

a. $\infty$
b. zero
c. p
d. $\frac{Cp}{Cv}$

107: Two systems are in thermal equilibrium the quantity which is common for them is

a. heat
b. momentum
c. specific heat
d. temperature

108: The height of a water spring is 50m. The difference of temperature at the top and bottom of the spring will be

a. $\mathbf{0}.\mathbf{117}\degc$
b. $1.17\degc$
c. $0.437\degc$
d. $11.7\degc$

109: The temperature of a black body corresponding to which it will emit energy at the rate of 1 watt/cm^2 will be

a. $\mathbf{650}\mathbit{K}$
b. 450K
c. 350K
d. 250K

110: If a piece of metal is heated to an absolute temperature T and then put in an enclosure at absolute temperature T, then the heat generated in the atmosphere will be proportional to

a. $\left(T-\ t\right)^4$
b. $\mathbit{T}^\mathbf{4}-\ \mathbit{t}^\mathbf{4}$
c. $T^2-t^2$
d. $T^3-t^3$

111: If the pressure of a gas is doubled then its thermal conductivity will

a. remains constant
b. decrease
c. decrease exponentially
d. increase

112: The color of a distant star in the sky is an indication of its

a. size
b. temperature
c. distance
d. frequency

113: The ratio of amplitudes of radiation emitted by a cylindrical source at distances 2r and 18r from its axis will be

a. 1:3
b. 2:1
c. 1:1
d. 3:1

114: A hot body will emit radiations more rapidly if its surface is

a. black and polished
b. white and polished
c. black and rough
d. white and rough

115: If the amount of heat incident upon a body is X calories and it absorbs Y calories out of it, then the coefficient of absorption will be

a. $X\ +\ Y$
b. XY
c. Y/X
d. $\frac{X}{Y}$

116: There is a small hole in a hollow container. At what temperature should it be maintained in order that it emits one calorie of energy per second per meter2

a. 10K
b. $\mathbf{100}\mathbf{K}$
c. 200K
d. 500K

117: In which part of the electromagnetic spectrum the heat radiations lie

a. visible
b. violet
c. ultraviolet
d. infrared

118: The correct relation between the intensity of radiation (I) and distance (d) from the point source is

a. $I\propto\frac{1}{d}$
b. $I\propto\ d$
c. $\mathbit{I}\propto\frac{\mathbf{1}}{\mathbit{d}^\mathbf{2}}$
d. $I\propto d^2$

119: When a yellow piece of glass is heated in dark room, then it emits

a. yellow colour
b. red colour
c. blue colour
d. green colour

120: If the temperature of a black body is increased by 50% then the amount of radiation emitted
by it will

a. decreased by 50%
b. increased by 50%
c. increased by 400%
d. decreased by 400%

121: A piece of red glass is heated till it starts shining in a dark room. The colour of this shining glass will be

a. violet
b. orange
c. green
d. red

122: The radiation force due to source of power P on a perfectly reflecting surface will be

a. $\frac{p}{3c}$
b. $\frac{\mathbf{2}\mathbit{p}}{\mathbit{c}}$
c. $\frac{p}{2c}$
d. $\frac{p}{c}$

123: The value of solar constant is approximately

a. $1340watt\ /m^{-2}$
b. $430watt/m^2$
c. $340watt/m^2$
d. $\mathbf{1388}\mathbit{watt}/\mathbit{m}^{-\mathbf{2}}$

124: The material of prism used for obtaining spectrum of heat radiationa is

a. rock salt
b. quartz
c. flint glass
d. crown glass

125: Fraunhofer’s lines are the result of which of the following phenomena of radiation

a. scattering
b. compression
c. emission
d. absorption

126: On which of the following laws, the constant volume thermometer works

a. Gay Loussac’s law
b. Dalton’s law
c. Boyle’s law
d. Charles’s Law

127: How is the velocity of thermal radiations (v) related to the velocity of light (c)

a. vc
c. v=c
d. relation depends on wavelength

128: The Kirchhoff’s law leads to the conclusion that the good radiators of thermal radiations are

a. good absorbers
b. bad absorbers
c. thermal insulators
d. none of these

129: Corresponding to a given temperature, there is a wavelength λ_m for which the intensity of heat tradition is

a. maximum
b. constant
c. zero
d. minimum

130: On which one of the factors do the nature of the thermal radiation depends inside an enclosure?

a. size of enclosure
b. temperature
c. nature of the wall
d. colour of the walls

131: Thermal radiations are similar to

a. $\alpha rays$
b. $\mathbf{X \ rays}$
c. cathode rays
d. none of these

132: Who explained the Fraunhofer lines in the spectrum of solar radiations

a. Wein
b. Fraunhofer
c. Stefan
d. Kirchhoff

133: Two stars X and Y emits yellow and blue lights. Out of these whose temperature will be more

a. that of Y
b. that of X
c. that of both
d. may be X or Y

134: If the temperature of a body increases by 2% then energy radiated will increase by

a. 2%
b. 8%
c. 4%
d. 16%

135: If the rate of emission of heat radiation of an ideal black body is made 16 times then it’s final temperature will become

a. half
b. doubled
c. 4 times
d. 8 times

136: Out of the following, which body is not an ideal black body

a. Wien’s black body
b. Ferry’s black body
c. coal
d. sun

137: When the temperature of a body is equal to that of the surroundings then the body appears

a. in thermal equilibrium
b. red
c. cold
d. hot

138: The hot water pipes used to heat up the room are painated

a. white
b. yellow
c. red
d. black

139: On increasing the temperature of a body the frequency (f_{max}\ ) corresponding to maximum emission of radiation will

a. increase
b. decrease
c. first decrease then increase
d. remains constant

140: The coefficient of transmission for an ideal black body is

a. infinity
b. zero
c. 1
d. more than one

141: The theoretical explanation of black body spectrum was given by

a. Lumer and Pringsheim
b. Plank
c. Stefan
d. Wein

142: The wavelength of yellow light is equal to the following mean of wavelengths of violet and red light

a. square of mean
b. arithmetic mean
c. geometric mean
d. harmonic mean

143: The amount of radiation emitted by a black body depends on its

a. size
b. mass
c. temperature
d. density

144: The unit of Wien’s constant is

a. $\mathbit{m}\mathbit{K}^{-\mathbf{1}}$
b. $cmK^{-1}$
c. $m^2K^{-1}$
d. $mK^{-1}$

145: The unit of Newton’s cooling constant is

a. $cal/s$
b. $\mathbf{cal} / \mathbf{s}\mathbf{o}^\mathbf{C}$
c. $cal/ \degc$
d. $o/C$

146: The frequency of ultraviolet rays is

a. ${\mathbf{10}}^{\mathbf{14}}\mathbf{Hz}$
b. ${10}^4Hz$
c. ${10}^8Hz$
d. ${10}^{10}Hz$

147: The solar heat and light reach the earth via

a. radiation
b. conduction
c. convection
d. all of these

148: Prevost’s theory of heat exchange is not applicable at temperature

a. $0^oR$
b. $0^oC$
c. $\mathbf{0}\mathbit{K}$
d. $0\degf$

149: The time taken by the solar radiations to reach earth is approximately

a. $8.3\ hr$
b. $1.3\ min$
c. $\mathbf{8}.\mathbf{3}\ \mathbit{min}$
d. $8.3\ sec$

150: The wavelength corresponding to maximum emission of solar radiations is

a. 8000A
b. $\mathbf{4753}\mathbit{A}$
c. 457A
d. 753A

151: If the temperature of an iron rod is doubled then the amount of radiation emitted by it, as compared to its initially value, becomes

a. $\frac{1}{2}$
b. equal
c. 4 times
d. 16 times

152: The energy of a photon of wavelength 6000 A in eV will be

a. 1.o6eV
b. 0.2o6eV
c. $\mathbf{2}.\mathbf{o}\mathbf{6}\mathbf{eV}$
d. 2oeV

153: If the temperature of the sun is doubled then the maximum emission wavelength as compared to its initial value will be

a. $\frac{1}{4}$
b. $\frac{\mathbf{1}}{\mathbf{2}}$
c. double
d. 4 times

MCQ's with Answers