NET, IAS, State-SET (KSET, WBSET, MPSET, etc.), GATE, CUET, Olympiads etc.: Physics MCQs (Practice_Test 9 of 35)

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  1. An electron having kinetic energy T is moving in a circular orbit of radius R perpendicular to a uniform Magnetic induction B. If kinetic energy is doubled and magnetic induction is tripled, The radius will become
    1. R ′
    2. R ′
    3. R ′
    4. R ′
  2. If in the first Bohr orbit of a hydrogen atom the total energy of the electron is-21.76 × 10 − 19 J, then its potential energy will be
    1. -43.52 × 10 − 19 J
    2. -21.76 × 10 − 19 J
    3. -10.88 × 10 − 19 J
    4. -13.60 × 10 − 19 J
  3. Consider the following substances, which are frequently used as a source of electrons:
    1. Magnesium
    2. Calcium
    3. Tungsten
    4. Platinum
    • The correct sequence of the above substances in increasing order of their work functions is
      1. 1,2, 3,4
      2. 2,1, 3,4
      3. 2,1, 4,3
      4. 1,2, 4,3
  4. The de-Broglie wavelength of material particles which are in thermal equilibrium at temperature T is
    1. h⟋sqrt 2mkT
    2. h⟋sqrt 2 mkT
    3. h-mkT
    4. h⟋sqrt2 kT
  5. The phase velocity (Vp) and the group velocity (Vg) of a de-Broglie wave, in free space (speed of light is c) are related as
    1. Vp⟋Vg = sqrt2
    2. Vp. Vg = C2
    3. Vp⟋Vg = 0.5
    4. Vp Vg = 2C2
  6. In Compton scattering, the incident photon will lose maximum energy if it is scattered at an angle of:
    1. 0
    2. 60
    3. 90
    4. 180
  7. In one of the radioactive decay chains we come across the element 22688 Ra. The final product of the chain is 20682 Pb. The number of a and b-is emitted
    1. 3 a and 6b-
    2. 4 a and 5b-
    3. 5 a and 4b-
    4. 6 a and 6b-
  8. At time t. = 0, N1 nuclei of decay constant l1 and N2 nuclei of decay constant l2 are mixed. The decay rate of the mixture is
    1. N1 N2 e- (l1 + l2) t
    2. (N1⟋N2) e- (l1 − l2) t
    3. (N1 N2 e-l1t + N2 l2 e-l 2t)
    4. N1⟋N2 e- (l1 + l2) t
  9. The nuclear reaction is an example of
    1. nuclear chain reaction
    2. successive disintegration
    3. pair production
    4. artificial radioactivity
  10. Which one of the following particles is a lepton?
    1. Neutron
    2. Proton
    3. Electron
    4. Lambda
  11. Match List I with List II and select the correct answer:
    Table Supporting: NET, IAS, State-SET (KSET, WBSET, MPSET, Etc.) , GATE, CUET, Olympiads Etc. : Physics MCQs (Practice_Test 9 of 35)
    List-I (Process)List-II (Approximate Energy released in mV)
    1. Fission of one uranium nucleus
    2. Formation of one helium nucleus by Fission
    3. Formation of a compound nucleus
    4. Formation of a deuteron by the
    1. Energy 2
    2. Energy 8
    3. Energy 200 by the capture of a neutron
    4. Energy 28 captures of a neutron by a proton
    • A
    • B
    • C
    • D
        • 3
        • 4
        • 2
        • 1
        • 2
        • 4
        • 1
        • 3
        • 4
        • 2
        • 3
        • 1
        • 3
        • 1
        • 2
        • 4
  12. Under space charge condition with the plate voltage Eb = 100 V and the permanence K = 104 (In S. I unit) , the plate current in a diode will be
    1. 10 − 6 mA
    2. 10 mA
    3. 102 mA
    4. 106 mA