Chapter # 17 Advent of Modern Physics

PHYSICS

CHAPTER # 17 Advent of Modern Physics

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2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

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Modern physics came into existence due to: a) Einstein special theory of relativity and quantum mechanics b) Maxwell’s theory of light c) Newtonian mechanics d) Huygen’s wave theory of light All motions are: a) Absolute b) Relative c) Uniform d) None of these A set of co-ordinate axis with respect to which measurements are made is called: a) Frame of reference b) Inertial frame of reference c) Non-inertial frame of reference d) None of these An inertial frame of reference is that one: a) Which moves with uniform velocity on earth b) Which is at rest c) Which has zero acceleration d) All of these A non-inertial frame of reference is that one: a) Which has zero acceleration b) Which has some acceleration c) Which is always at rest d) None of these The classical physics is based upon the laws of: a) Newtonian mechanics b) Quantum mechanics c) Wave mechanics d) None of these According to Maxwell’s theory, light consists of: a) Magnetic field b) Electric field c) Electric and magnetic field d) None of these Light was considered as electromagnetic wave by the scientist: a) Newton b) Huygen c) Faraday d) Maxwell Which one of the following require a material medium for their propagation: a) Sound waves b) Light waves c) Heat waves d) X-rays The existence of “Ether wind” was experimentally rejected by: a) De-Broglie b) Faraday c) Michelson and Morley d) Einstein In 1905, the theory of relativity was proposed by: a) Einstein b) Morley c) Michelson d) De-Broglie According to Einstein’s theory of relativity: a) All laws of physics are the same in every inertial frame of reference b) Speed of light in free space is a universal constant c) Speed of light is independent of the speed of observer d) All of the above Which one of the following physical quantities changes with relativistic speed: a) Mass b) Length c) Time d) All of these The mass of an object will be doubled at speed: a) 2.6  108 m/s b) 1.6  108 m/s -8 c) 2.6  10 m/s d) None of these According to special theory of relativity, the relation between rest mass and moving mass is given by: mo a) m = mo

V 1 ( ) 2 C

b) m =

V 1 ( ) C

c) m =

Bahadur Ali Qureshi

1 d) m = mo

B A D B A C D A C A

D

D A

C

mo V 1 ( ) 2 C

A

V C

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CHAPTER # 17 Advent of Modern Physics 16. According to the special theory of relativity, the relation between the length of the rest object and moving object is given by: lo a) l = lo

V 1 ( ) 2 C 1

18. 19.

20. 21.

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b) l =

V 1 ( ) 2 C

A

V C

c) l = d) None of the above If a material object moves with speed of light its mass becomes: a) Equal to its rest mass b) Double of its rest mass c) Infinite d) Zero Einstein’s mass and energy relation is: a) E = mc2 b) E = mc m m2 c) E = c d) E = c One kilogram mass will be equivalent to the energy: a) 9  108 Joules b) 9  1016 Joules 10 c) 9  10 Joules d) 6  1016 Joules If rest mass of particle is mo and relativistic mass is m, then its kinetic energy (K.E) is: 1 2 a) mc b) 2 mv2 1 c) (m-mo)c2 d) 2 (m-mo)c2 The relativistic changes in mass, length and time in daily life are not observed because: a) The mass of the objects are very large b) The size of the objects are very small c) The speed of the objects are very small as compared to speed of light d) None of the above If the energy of the photon is E, it is equivalent to mass: E C2 2 a) C b) E 2 c) EC d) EC The discrete nature of radiation was introduced by: a) Hertz b) Max Planck c) J.J. Thomson d) Rayleigh-Jean The electron was discovered by: a) Milikan b) J. J. Thomson c) Chadwick d) Bohr An ideal black body is: a) The most efficient radiator b) A perfect absorber of radiation c) A body whose absorber power is unity d) All of the above As the temperature of black body is raised, the wavelength corresponding to maximum intensity: a) Shifts towards longer wavelength b) Shifts towards shorter wavelength c) Remains the same d) None of these Planck’s concept was used by: a) J. J. Thomson b) Rutherford c) Einstein d) Hertz Radiations are always emitted or absorbed in the form of packets of energy. This is the statement of: a) Rayleigh-Jean’s law b) Wein’s displacement law c) Stefan’s law d) Planck’s quantum law In 1900, who proposed a formula which explained in detail the whole shape of the black body spectrum for all wavelengths: a) Rayleigh b) Wein c) Einstein d) Max Planck Who proposed quantum theory of radiations? a) Faraday b) Newton c) Einstein d) Planck Black body can be made by: a) A surface coated with lamp black b) A hollow cavity within a solid body c) A highly polished black body d) A tungsten filament Bahadur Ali Qureshi

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C

A

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C

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B B D B C D

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CHAPTER # 17 Advent of Modern Physics

33. 34.

35. 36. 37.

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51.

A good absorber of heat radiation would be: a) A white towel c) A polished plate Absorption power of perfect black body is: a) Zero

b) Black wool blanket d) None of the above

B

b) Infinite 1 c) One d) 2 On a hot day or in hot climates white clothes are worn because they are good: a) Reflectors b) Absorbers c) Radiators d) Emitters Which theory explains that energy exchange takes place in discrete “bundles” or “quanta”? a) Special theory of relativity b) Quantum theory c) Corpuscular theory d) Bohr’s theory Mathematically quantum theory is stated as: a) E = mC2 b) E = hf C c) f =  d) None of the above A single quantum of electromagnetic radiation is: a) Photon b) Proton c) Meson d) Positron Light consists of particle wave called: a) Proton b) Electron c) Neutron d) Photon Rest mass of photon is: a) Infinite b) Zero c) Equal to proton d) None of the above The name of photon for a quantum of light was proposed by: a) Bohr b) Ampere c) Thomson d) Planck The magnitude of Planck’s constant is: a) 1.6  10-19 Joule-second b) 6.63  10-34 Joule-second -54  c) 6.63 10 Joule-second d) None of the above The velocity of photon is: a) 3  108 ms-1 b) 3  108 cms-1 c) 3  102 ms-1 d) 6  108 ms-1 The energy of photon is given by: 1 a) E = 2 mV2 b) E = hf c) E = moC2 d) E = Voe The phenomenon of electron ejection by light is called: a) Photoelectric effect b) Compton effect c) Photo cell d) The uncertainty principle Einstein was awarded Nobel prize for the explanation of photoelectric effect in: a) 1905 b) 1921 c) 1925 d) 1934 The photoelectric effect was explained by: a) Einstein b) Planck c) Hertz d) Lenar  In photoelectric effect, -rays are completely absorbed with the emission of: a) Protons b) Positrons c) Electrons d) Neutrons In photoelectric effect, the light exhibits: a) Wave nature b) Particle nature c) Both particle and wave nature d) All of the above A photo-electric cell operates because of: a) Compton effect b) Photoelectric effect c) Photo refraction d)  -rays counter The amount of energy required to eject an electron from metal surface is called: a) Compton effect b) Threshold frequency c) Work function d) Pair production Bahadur Ali Qureshi

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B

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B

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CHAPTER # 17 Advent of Modern Physics

52. 53. 54. 55. 56. 57. 58. 59. 60.

61. 62. by:

Joule-second is the unit of: a) Heat b) Energy c) Power d) Planck’s constant In which of the following phenomenon, the electromagnetic radiations show particle property: a) Interference b) Photoelectric effect c) Diffraction d) None of the above Phenomenon in which electric charges (electrons) are emitted from hot bodies is known as: a) Photoelectric emission b) Thermionic emission c) Oscillatory current d) None of the above Ions emitted from hot metals are called: a) Electrons b) Protons c) Neutrons d) None of the above In photoelectric effect, the threshold frequency is: a) Different for different materials b) Same for all materials c) Neither different nor the same d) Random Amount of K.E. of emitted photoelectrons depends upon: a) Temperature of surface b) The intensity of incident light c) Frequency of incident light d) All of the above A device based on photoelectric effect is called: a) Photo cell b) Battery c) Dry cell d) Photo diode The process of scattering of an X-ray photon by an electron is called: a) Compton effect b) Photoelectric effect c) Pair production d) None of the above The momentum of photon of frequency f is: hc fc f a) b) h hf c) c d) hfc Compton effect is a phenomenon in which electromagnetic waves (radiation) exhibit: a) Wave nature b) Particle nature c) Particle wave nature d) None of the above Compton effect gives a relation between original frequency ‘f’ and scattered photon ‘f’ which is

a)

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h 1 1 2 f  = f + m o c (1 – cos  ) h

D B B A A C A A

C

B given

h m c2 b) f  = f + o (1 – cos  ) h 1 1

A

m c b)  = o (1 - sin  ) h m c d)  = o (1 + cos  )

D

m c2 m c2 c) f = f  + o (1 – cos  ) d) f = f  + o (1 – cos  ) In Compton scattering, the change in the wavelength is given by: h h m c2 a)  = o cos  h m c c)  = o (1 - cos  ) The momentum of moving photon is:

h a) Zero b) P = 2 h  c) P =  d) P = h Disintegration of photon on striking a nucleus into an electron and positron is known as: a) Compton effect b) Annihilation of matter c) Pair production d) All of the above The materialization of energy takes place in the process: a) Annihilation b) Pair production c) Compton effect d) Photoelectric effect Positron is an anti-particle of: a) An electron b) A neutron c) A psi-meson d) None of the above Bahadur Ali Qureshi

C

C B A -4-

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68. 69. 70. 71.

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CHAPTER # 17 Advent of Modern Physics The relation, hf = 2moc2 + KEe- + KEe+, holds a: a) Pair production b) Compton effect A c) Photoelectric effect d) Photo cell The minimum energy required by a photo to create an electron-positron pair is: a) 3 Mev b) 4 Mev C c) 1.02 Mev d) Zero The reverse process of pair production is called: a) Pair Annihilation b) Compton effect A c) Photoelectric effect d) None of the above The rest mass energy of an electron is: a) 9.11  10-31 J b) 6.7 Mev C c) 0.511 Mev d) 1.67  10-27 J If a particle of mass m is moving with a speed v, then De-Broglie’s wavelength ‘  ’ associated with it will be: 3 h B mV mV   a) = b) = 2 mV c)  = h d)  = mV The relation of uncertainty principle between energy and time is given by: a) ( E ) ( P )  h b) ( E ) ( t )  h c) ( P ) ( t )  h d) ( x ) ( P )  h The relation of uncertainty principle between position and momentum is given by: a) ( x ) ( P )  h b) ( x ) ( t )  h c) ( E ) ( t )  h d) ( P ) ( E )  h

Bahadur Ali Qureshi

B

A

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