Q.1
What is the de Broglie wave length of an electron accelerated through 40kV?
  • a)614 pm
  • b) 61.4 pm
  • c)6.14 pm
  • d)0.614 pm
Q.2
Matter waves are similar in nature to
  • a) X-rays
  • b) γ-rays
  • c)Cathode rays
  • d)none of the above
Q.3
The propagation constant of the de Broglie waves associated with an electron is
  • a) Proportional to its mass
  • b) Proportional to its momentum
  • c) Proportional to its energy
  • d) Inversely proportional to its energy
Q.4
The wavelength of the matter wave is independent of
  • a)mass
  • b) velocity
  • c)momentum
  • d)charge
Q.5
An electron accelerated by a potential difference of V volt posses a de Broglie wave length λ. If the accelerating potential is increased by a factor of 4, the de-Broglie wavelength of the electron will be
  • a) Remains unchaged
  • b) Becomes 4 times
  • c)Becomes Half
  • d)Becomes double
Q.6
A photon and electron have same wave length then
  • a) photon has greater momentum
  • b) electron has greater momentum
  • c)they have the same momentum
  • d)none of the above
Q.7
The function of the crystal in Davisson and Germer experiment is
  • a) To reflect the electron beam
  • b) To refract the electron beam
  • c) To diffract the electron beam
  • d) To focus the electron beam
Q.8
The interplanar spacing of crystal is 1.225 Å. the maximum order of diffraction of electrons accelerated through a potential difference of 10 kV is
  • a) 1
  • b) 20
  • c)100
  • d)1000
Q.9
A particle of mass 1kg is moving with a velocity of 1m/s. The de-broglie wavelength associated with it will be
  • a) h
  • b) h/2
  • c) h/4
  • d) 2h
Q.10
Which of the following graph is correct
  • a)
    ch-9_qn-145choice_img_no1.png
  • b)
    ch-9_qn-145choice_img_no2.png
  • c)
    ch-9_qn-145choice_img_no3.png
  • d)
    ch-9_qn-145choice_img_no4.png
Q.11
de-Broglie wavelength associated with a neutron at T degree Kelvin is
  • a) (1.82 / T )Å
  • b) (1.82/√T) Å
  • c)(30.7/T ) Å
  • d)(30.7/√T ) Å
Q.12
The stopping potential for electron beam of de-Broglie wavelength of 1 Å
  • a)12.3Volts
  • b) 123 Volts
  • c)151 Volts
  • d)1505 Volts
Q.13
The pulse duration of radar is 0.25µs. The uncertainty in the frequency of photons is
  • b) 6.6 × 104
  • c) 6.4 × 105
  • a) 4.2 × 10⁻²⁸
  • d) 4.2 × 10⁻⁴
Q.14
Uncertainty Principle states that the error in measurement is due to
  • a)Dual nature of particles
  • b) Due to small size of particles
  • c)Due to large size particles
  • d)Due to error in measurement
Q.15
Work function of a photoelectric material is 3.3eV. The threshold frequency will be equal to [ CPMT 1986]
  • a) 8 × 1010Hz
  • b) 4 × 1014 Hz
  • c)8×1014 Hz
  • d)4 × 1020 Hz
Q.16
For light of wavelength 5000Å , the photon energy is nearly 2.5 V. For X-rays of wavelength 1Å, the photon energy will be close to [ CPMT 1987]
  • a)2.5 ÷ 5000 eV
  • b) 2.5 ÷ (5000)2 eV
  • c)2.5 × 5000 eV
  • d)2.5 × (5000)2 eV
Q.17
In order to increase the kinetic energy of ejected photoelectrons, there should be an increases in [ PMT 1987]
  • a) intensity of radiation
  • b) wavelength of radiation
  • c) frequency of radiation
  • d) both the wavelength and intensity of radiation
Q.18
When a certain metallic surface is illuminated with monochromatic light of wavelength λ, the stopping potential for photoelectric current is 3Vo. When the same surface is illuminated with the light of wavelength 2λ, the stopping potential is Vo. The threshold wavelength for the surface for photoelectric effect is [ MPPMT 1987]
  • a)4λ/3
  • b) 4λ
  • c)6λ
  • d)8λ
Q.19
The specific charge for positive rays is much less than that for cathode rays. This is because [ C.P.M.T 1990]
  • a) Positive rays are positively charged
  • b) charge on positive rays is less
  • c)mass of positive rays is much larger
  • d)experimental method is wrong
Q.20
Light of wavelength 4000Å is incident on a metal plate whose work function is 20eV. The maximum kinetic energy of the emitted photoelectrons would be [ CPMT 1990]
  • a) 0.5 eV
  • b) 1.1 eV
  • c)1.5 eV
  • d)2.0 eV
Q.21
A proton is accelerated through one volt the increase in its kinetic energy is approximately [ CPMT 1993]
  • a) 1/1870 eV
  • b) 1870 eV
  • c) 1 eV
  • d) 300 eV
Q.22
An electron enters a region where magnetic induction B and electric field E are mutually perpendicular to one another then..
  • a)it will always move in the direction of B
  • b) it will always move in the direction of E
  • c)it always possessses circular motion
  • d)it can go undeflected also
Q.23
The threshold wavelength for photoelectric effect of a metal is 6500Å. The work function of the metal is approximately
  • a) 2 eV
  • b) 1 eV
  • c)0.1 eV
  • d)3 eV
Q.24
Threshold frequency for photoelectric effect on sodium corresponds to a wavelength 5000 Å. Its work function is ..
  • a) 15 joule
  • d) 4 ×10+19 joule
  • b) 10 × 10⁻¹⁰ joule
  • c) 4 × 10⁻¹⁹ joule
Q.25
Number of ejected photoelectrons increases with increase
  • a)in intensity of light
  • b) in wavelength of light
  • c)in frequency of light
  • d)never
Q.26
The ratio of momentum of electron and an alpha particle which are accelerated from rest through a potential difference of 100 volt is [ CEE 1994]
  • a) 1
  • b) √(2me / mα)
  • c)√( me / mα)
  • d)√(me /2mα)
Q.27
Doubly ionised Helium atoms and Hydrogen ions are accelerated from rest through the same potential drop. The ratio of the final velocities of the Helium and the Hydrogen ions is
  • a)2
  • b) √2
  • c)1/2
  • d)1/√2
Q.28
Gases begin to conduct electricity at low pressure because
  • a) the lectrons in atoms can move freely at low pressures
  • b) atoms break up into electrons and protons
  • c) colliding electrons can acquire higher kinetic energy due to increased mean free path leading to ionization of atoms
  • d) at low pressure gases turn into plasma
Q.29
Photoelectric effect is due to
  • a)wave nature of light
  • b) particle nature of light
  • c)both a and b
  • d)none of these
Q.30
If the frequency of light in a photoelectric experiment is doubled the stopping potential will [ CPMT 1994]
  • a) be doubled
  • b) be halved
  • c)become more than double
  • d)become less than double
0 h : 0 m : 1 s