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The MCQs below are drawn from the Physics subject category.
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1571
A Kα x-ray emitted by one hydrogen atom strikes a second hydrogen atom and undergoes photoelectric absorption with an L shell electron. What energy does the effected electron have?
A. 13.6 eV
B. 10.2 eV
C. 6.8 eV
D. 3.4 eV
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Correct Option
Explanation
Answer taken from the provided OCR answer key in the block.
1572
What is the change in the atomic number from 'W' to 'Z'?
A. Decreases by 3
B. Decreases by 5
C. Increases by 3
D. Increases by 5
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Correct Option
Explanation
The OCR indicates option B; the decay sequence shown results in a net decrease of 3 in atomic number.
1573
The part of theory of relativity which deals with accelerated bodies is called
A. Galilean theory of relativity
B. general theory of relativity
C. Lorentz's theory of relativity
D. special theory of relativity
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Correct Option
Explanation
General relativity extends relativity to include acceleration and gravitation, unlike the special theory which covers inertial frames.
1574
With regard to the production of thermal neutrons which of the following statements is true?
A. The collision of neutron takes place till its velocity becomes zero.
B. The neutron gains velocity when it collides with the moderator.
C. The slow neutrons are passed through moderators.
D. The collision of neutrons with hydrogen takes place till their kinetic energies are the same.
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Correct Option
Explanation
Thermal (slow) neutrons are produced by passing faster neutrons through moderators which slow them down, so A is correct.
1575
208. The energy of γ-rays emitted in the β-decay of 26Al is (given Qβ = 2.86 MeV)
A. 1.78 KeV
B. 17.8 MeV
C. 1.78 MeV
D. 1.78 BeV
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Correct Option
Explanation
Using the given decay energy (2.86 MeV) and energy conservation for the β-decay, the γ-ray energy corresponds to 1.78 MeV, which matches option A.
1576
The mass of an electron having K.E. 1.5 MeV will be
A. 358 × 10^-31 kg
B. 9.1 × 10^-31 kg
C. 35.8 × 10^-31 kg
D. 3.58 × 10^-31 kg
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Correct Option
Explanation
Total energy = rest energy (0.511 MeV) + KE (1.5 MeV) ≈ 2.011 MeV, which corresponds to ≈3.58 × 10^-30 kg (35.8 × 10^-31 kg), matching option C.
1577
If the material through which the radiation has to pass is denser, its range will:
A. Become independent of the density
B. Be shorter
C. Be longer
D. Increase exponentially
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Correct Option
Explanation
Greater material density causes more interactions and energy loss, reducing penetration range, so 'Be shorter' (option A) is indicated by the OCR tick.
1578
What was the fissionable material used in bomb dropped at Nagasaki (Japan) in the year 1945?
A. Neptunium
B. Uranium
C. Beryllium
D. Plutonium
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Correct Option
Explanation
The Nagasaki bomb ('Fat Man') used plutonium (Pu-239) as its fissile material.
1579
Cosmic rays
A. Are charged particles
B. Are uncharged particles
C. Can be charged as well as uncharged
D. None of these
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Correct Option
Explanation
Cosmic rays are predominantly high-energy charged particles (such as protons and atomic nuclei) arriving from space.
1580
Kα characteristic X-ray refers to the transition
A. n = 4 to n = 2
B. n = 2 to n = 1
C. n = 3 to n = 2
D. n = 3 to n = 1
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Correct Option
Explanation
Kα lines correspond to an electron transition from the L-shell (n=2) to the K-shell (n=1).
