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CBSE Questions for Class 12 Medical Physics Dual Nature Of Radiation And Matter Quiz 9 - MCQExams.com

Which of the following figures represent the variation of particle momentum and the associated de-Broglie wavelength?
The de Broglie wavelength λ associated with a  proton increases by 25%. If its momentum is decreased by p0. The initial  momentum was:
  • 4p0
  • p04
  • 5p0
  • p05
A monochromatic beam of electromagnetic radiation has an intensity of 1W/m2 . Then the average number of photons per m3 for  a 10MeV γ ray is ? 
  • 4166
  • 3000
  • 5000
  • 2083
When light of intensity 1 W/m2 and wavelength 5×107m is incident on a surface, it is completely absorbed by the surface. If 100 photos emit one electron and area of the surface is 1 cm2, then the photoelectric current will be
  • 2 mA
  • 0.4 μA
  • 4.0 mA
  • 4 μA
The De-Broglie wavelength associated with electrons revolving round the nucleus in a hydrogen atom in ground state, will be-
  • 0.3 A
  • 3.3 A
  • 6.62 A
  • 10 A
The de Broglie wavelength corresponding to the root-mean-square velocity of hydrogen molecules at temperature 20o C is 
  • 3.3Ao
  • 1.04Ao
  • 126Ao
  • 34Ao
The ratio of dBroglie wavelength of molecular of hydrogen and oxygen kept in two vessels separately at 27oC and 127oC respectively is:
  • 43
  • 332
  • 83
  • 18
When a point source of light is at a distance of 50cm from a photoelectric cell, the cut -off voltage is found to be V0.If the same source is placed at a distance of 1m from the cell,then the cut -off voltage will be:
  • V0/4
  • V0/2
  • V0
  • 2V0
A proton is accelerated through 225\, V. Its de Brogile wavelength is:
  • 1.91\, pm
  • 0.2\, pm
  • 3\, pm
  • 0.4 \,nm
 what is the angular momentum of an electron of de-broglie wavelength \lambda ? given r is the radius of orbit.
  • \dfrac{{rh}}{\lambda }
  • \dfrac{{2rh}}{\lambda }
  • \dfrac{{3rh}}{\lambda }
  • \dfrac{{4rh}}{\lambda }
According to de Broglie, wavelength of electron in second orbit is 10^{-9} meter. Then the circumference of orbit is :-
  • 10^{-9}
  • 2 \times 10^{-9}
  • 3 \times 10^{-9}
  • 4 \times 10^{-9}
Threshold wavelength of tungsten is 2300 angstrom. If ultraviolet light of wavelength 1800 angstrom is incident on it, then the maximum kinetic energy of photoelectrons would be ?
  • 1.5 eV
  • 2.5eV
  • 3.0 eV
  • 5.0eV
A particle is dropped from a height H. The de-Broglie wavelength of the particle as a function of height is proportional to
  • H
  • H\dfrac{1}{2}
  • H^o
  • H\dfrac{-1}{2}
A photon and an electron both have wavelength 1A^{o}. The ratio of energy of photon to that of electron is
  • 1
  • 0.012
  • 82.7
  • 10^{-10}
The de-Broglie wavelength of an electron is the same as the wavelength of a photon. The K.E of photon is 'x' times the K.E of the electron,then 'x' is (m-mass electron ,h- planck's constant,c-velocity of light)
  • \dfrac{hc}{2\lambda m}
  • \dfrac{2m\lambda c}{h}
  • \dfrac{2\lambda c}{hm}
  • \dfrac{2\lambda m}{ch}
The radio of deBroglie wavelengths of a proton and an alpha particle of same energy is
  • 1
  • 2
  • 4
  • 0.25
A chlorine molecule with an initial velocity of 600ms^{-1} absorbs a photon of wavelength 350 nm and is then dissociated into two chlorine atoms. One of the atoms is detected moving perpendicular to the initial direction of the molecule and having a velocity of 1600ms^{-1}. The binding energy of the molecule is (approx)? [Neglect the momentum of the absorbed photon. The relative atomic mass of chlorine is 35]
  • 3.36\times 10^{-17}J
  • 3.36\times 10^{-19}J
  • 3.36\times 10^{-21}J
  • 3.36\times 10^{-28}J
Electron has energy of 100 { e }{V } what will be its wavelength
  • 1.2{ \mathring { A } }
  • 10 { \mathring { A } }
  • 100 { \mathring { A } }
  • 1 \mathring { A }
The de Broglie wavelength of an electron moving with a velocity 1.5 \times{ 10 }^{ 8 }{ ms }^{ -1 } is equal to that a photon. The ratio of the kinetic energy of the electron to the that of the photon is 
  • 2
  • 4
  • \dfrac { 1 }{ 2 }
  • \dfrac { 1 }{ 4 }
A photon and an electron both have wavelength 1\mathring { A } . The ratio of energy of photon to that of electron is 
  • 1
  • 0.012
  • 82.7
  • { 10 }^{ -10 }
If the rest mass of an electron or positron is 0.51\ MeV, then the kinetic energy of each particle, in the electron-positron pair produced by a \gamma-photon of 2.42\ MeV, will be ?
  • 0.3\ MeV
  • 1.9\ MeV
  • 0.7\ MeV
  • 1.5\ MeV
An \alpha particle is moving in a circular path of radius in the presence of magnetic field B. The de-Broglie wavelength associated with the particle will be (q\rightarrow charge\quad on\quad \alpha \quad particle)
  • \cfrac { hr }{ qB }
  • \cfrac { hB }{ qr }
  • \cfrac { h }{ qBr }
  • \cfrac { h{ r }^{ 2 } }{ qB }
A photon and an electron have equal energy E. {\lambda _{photon}} \times {\lambda _{electron}} is proportional to:
  • E^{\dfrac{-3}{2}}
  • \frac{1}{{\sqrt E }}
  • \frac{1}{E}
  • Does not depend upon E.
De-Broglie wavelength associated with thermal neutrons at room temperature of 27^{0}C is :
  • 1.452\times 10^{-10}m
  • 2.57\times 10^{-10}
  • 0.452\times 10^{-10}m
  • 3.452\times 10^{-10}m
A particle of mass M at rest decays into particles of masses m_{1} \ and  \ m_{2} having non -zero velocities. The ratio of the de broglie wavelengths of the particles \lambda _{1}/\lambda _{2} is :
  • m _{1}/m _{2}
  • m _{2}/m _{1}
  • 1
  • m1.m2
The threshold frequency for a photosenstive metal is 7 \times 10 ^ { 13 } \mathrm { Hz}. If light of frequency 10 ^ {14 } \mathrm { Hz} is incident on this metal, then maximum kinetic energy of emitted electron is?
  • 4 \times 10 ^ { -20 } \mathrm {J}
  • 8 \times 10 ^ { -20 } \mathrm {J}
  • 2 \times 10 ^ { -20 } \mathrm {J}
  • 10 ^ { -20 } \mathrm {J}
The ratio of wavelength of deutron and proton accelerated through the same potential difference will be-
  • \dfrac { 1 }{ \sqrt { 2 } }
  • \sqrt { \dfrac { 2 }{ 1 } }
  • \dfrac { 1 }{ 2 }
  • \dfrac { 2 }{ 1 }
A source S_{1} is producing 10^{15} photons per second of wavelength 5000 A^o . Another source S_{2} is producing 1.02 \times 10^{15} photons per second of wavelength 5100 A^o .Then, \dfrac{(power \ of \ S_{2})}{(power \  of \ S_{1})} is equal to
  • 0.98
  • 1.00
  • 1.02
  • 1.04
If Bohr radius is r_{0}, the corresponding de Broglie wavelength of the electron is 
  • \left ( \dfrac{2\pi }{r_{o}} \right )
  • \left ( \dfrac{r_{o} }{2\pi } \right )
  • \left ( \dfrac{1}{2\pi r_{o}} \right )
  • {2\pi r_{o}}
Energy of a photon having wave number 1.00 cm^{-1} is 
  • 6.62\times 10^{-34} J
  • 1.99\times 10^{-23} J
  • 6.62\times 10^{-32} J
  • 6.62\times 10^{-36} J
Five elements A, B, C, D and E have work functions 1.2 eV, 2.4 eV, 3.6 eV , 4.8eV and 6.8 eV respectively. If light of wavelength 4000 A ^ { \circ } is allowed to fall on these elements, then photoelectrons are emitted by
  • A, B and C
  • A, B, C, D and E
  • A and B
  • Only E
An electron beam has a kinetic energy equal to 100\ eV. Find its wavelength associated with a beam, if mass of electron is 9.1 \times 10 ^ { - 31 }\ kg and  1 \text { eV } = 1.6 \times 10 ^ { - 19 } \mathrm { J }. (Planck's constant is 6.6 \times 10 ^ { - 34 } \mathrm { J-s } )
  • 24.6 \mathrm { A }^{o}
  • 0.12 \mathrm { A }^{o}
  • 1.2 A^{o}
  • 6.3 \mathrm { A }^{o}
Photoeelectric work-function of a metal is 1eV. Light of wavelength \lambda = 3000 \mathring { A } falls on it. The photoelectrons come out with maximum velocity:
  • 10 m/s
  • 10^3 m/s
  • 10^4 m/s
  • 10^6 m/s
K_1 and K_2 are the maximum kinetic energies of the photo electrons emitted when light of wave lengths \lambda_1 and \lambda_2 respectively are incident on a metallic surface. If \lambda_1 = 3\lambda_2 then
  • K_1 > \dfrac{K_3}{3}
  • K_1 < \dfrac{K_2}{3}
  • K-1 > 3K_2
  • K_2 = 3K_1
When an electron de-excited back from (n+1)^th state to n^th state in a hydrogen like atoms, wavelength of radiation emitted is \lambda_{1}(n>>1). In the same atom de-broglies wavelength associated with an electron in n^th state is \lambda_{2}. Then \dfrac{\lambda_{1}}{\lambda_{2}} is proportional to
  • \dfrac{1}{n}
  • n
  • n^{2}
  • n^{3}
When light is incident on surface, photo electrons are emitted. For photoelectrons:
  • The value of kinetic energy is same for all
  • Maximum kinetic energy do not depend on the
    wave length of incident light
  • The value of kinetic energy is equal to or less
    than a maximum kinetic energy
  • None of the above
The ratio of de-Broglie wavelengths of molecules of hydrogen and helium Which are at temperature 27^oC and 127^oC respectively is 
  • \dfrac { 1 }{ 2 }
  • \sqrt { \dfrac { 3 }{ 8 } }
  • \sqrt { \dfrac { 8 }{ 3 } }
  • 1
The velocity of photons is proportional to (where v = frequency) 
  • \dfrac { 1 } { \sqrt { v } }
  • v ^ { 2 }
  • \mathrm { v } ^ { 0 }
  • \sqrt { v }
If E_{1},E_{2},E_{3} and E_{4} the respectively kinetic energies of electron, decuteron proton and neutron having same de-Broglic wavelength, identity the correct in which those value would increase,
  • E_{2},E_{4},E_{3},E_{1}
  • E_{1},E_{3},E_{4},E_{2}
  • E_{2},E_{4},E_{1},E_{3}
  • E_{3},E_{1},E_{2},E_{4}
Find the maximum KE of photo electrons liberated from the surface of lithium by electron magnetic radiation whose electric component varies with time as \varepsilon =a\left( 1+\cos { \omega t }  \right) \cos { { \omega  }_{ 0 } } t where 'a' is a constant \left(\dfrac {\omega}{2\pi}\right) =6\times 10^{14}s^{-1} and \left(\dfrac {\omega _{0}}{2\pi}\right) =0.66\times 10^{14}s^{-1}, work function of lithium =2.39\ eV  
  • 0.72\ eV
  • 0.36\ eV
  • 0.603\ eV
  • 0.99\ eV
A hydrogen atom emits a photon corresponding to an electron transition from n =5 to n=The recoil speed of hydrogen atom is almost  (mass of proton = 1.6\times 10^{-27}\, kg)
  • 10\ ms^{-1}
  • 2\times10^{-2}\ ms^{-1}
  • 4\ ms{-1}
  • 8\times10^2\ ms^{-1}
If the debroglie wave-length of He at 927^{o}C is \lambda then de-brolie wave-length of CH_{4}(g) at 27^{o}C will be
  • \lambda
  • \dfrac {\lambda}{2}
  • \dfrac {\lambda}{4}
  • 2\lambda
The wavelength \lambda_{e} of an electron and \lambda_{p} of a photon of same energy E are related by
  • \lambda_{p} \propto \lambda_{e}^{2}
  • \lambda_{p} \propto \lambda_{e}
  • \lambda_{p} \propto \sqrt {\lambda_{e}}
  • \lambda_{p} \propto \dfrac {1}{\sqrt {\lambda_{e}}}
An electron is moving in { 2 }^{ nd } excited orbit of H-atom Radius of orbit in terms of de-Broglie wavelength \lambda of electron can be given as
  • \cfrac { \lambda }{ \pi }
  • \cfrac { 2\lambda }{ \pi }
  • \cfrac { 3\lambda }{ 2\pi }
  • \cfrac { \lambda }{ 2\pi }
The work function of a metal is 1.84\ eV. If the wavelength of incident photon is 4000 \mathring{A}, Then the approximate maximum kinetic energy of emitted photoelectron will be 
  • 1.25\ eV
  • 3.1\ eV
  • 0.58\ eV
  • 1.8\ eV
The debroglie wavelength of photoelectrons is 1\mathring {A}. Its accelerating potential is :
  • 150\ V
  • 15.3\ V
  • 12.3\ V
  • 13.6\ V
A parallel beam of uniform, monochromatic light of wavelength 2640 \overset { o }{ A } has an intensity of 100 W/m^2. The number of photons in 1 mm^3 of this radiation are -
  • 266
  • 335
  • 442
  • 555
The momentum of a photon is 2\times 10^{-16} gm-cm/sec. Its energy is
  • 0.61\times 10^{-26} erg
  • 2.0\times 10^{-26} erg
  • 6\times 10^{-6} erg
  • 6\times 10^{-8} erg
The de Broglie wavelength of a gas molecule at a temperature T K is:
  • \cfrac{h}{\sqrt{3mKT}}
  • \cfrac{h}{3mKT}
  • \cfrac{h}{\sqrt{2mKT}}
  • \sqrt{2mKT}
A particle of mass m kg and charge q coulomb is accelerated from rest through V volt: then the de-Broglie wavelength \lambda associated with it is given by 
  • \lambda = \frac{h}{\sqrt{mV}}
  • \lambda = \frac{h}{\sqrt{2mq}}
  • \lambda = \frac{h}{\sqrt{2mqV}}
  • \lambda = \frac{h}{\sqrt{2mV}}
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