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Showing 1671–1680
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1671
The photons emitted by nuclei range in energy up to several MeV, and are traditionally called:
A. Alpha rays
B. Beta rays
C. Gamma rays
D. None of these
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Correct Option
Explanation
High-energy photons emitted by nuclei are termed gamma rays, and the OCR indicates option C.
1672
β-rays is:
A. Electromagnetic radiation
B. Particles emitted from nucleus
C. Positively charged
D. All of these
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Explanation
Beta rays are electrons (or positrons) emitted from the nucleus, hence they are particles emitted from the nucleus.
1673
The process by which nuclei emit α, β and x-rays in order to attain stability is called
A. radioactive transmutation
B. radioactivity
C. radioactive disintegration
D. β-decay
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Correct Option
Explanation
Emission of alpha, beta and gamma (x) radiation by nuclei to attain stability is termed radioactivity.
1674
(144) Which of the following is a true statement about the modern QCD quark and gluon picture of the structure of matter?
A. The u, c, t quarks have charge -1/3e.
B. The d, s, b quarks have charge 2/3e.
C. The s, c and b quarks have special quantum numbers S, C, B.
D. All six quarks have been observed in a free unconfined state.
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Correct Option
Explanation
Strange, charm and bottom quarks carry the quantum numbers S, C and B respectively, which is a true statement (a).
1675
Photons with energy 5 eV are incident on a cathode C in a photoelectric cell. The maximum energy of emitted photoelectrons is 2 eV. When photons of energy 6 eV are incident on C, no photoelectrons will reach the anode A, if the stopping potential of A relative to C is
A. +3 V
B. -3 V
C. +4 V
D. -1 V
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Correct Option
Explanation
Work function φ = 5 eV - 2 eV = 3 eV; with 6 eV photons KEmax = 3 eV, so an anode potential of -3 V relative to cathode will just stop electrons.
1676
When a high energy neutron bombards a nucleus, producing another particle, the other particle released is
A. Proton
B. Electron
C. Positron
D. Gamma ray photon
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Correct Option
Explanation
A high-energy neutron can induce (n,p) reactions in which a proton is emitted from the target nucleus.
1677
Which of the following particles leave no trail in a cloud chamber?
A. Electrons
B. Protons
C. Neutrons
D. α-particles
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Explanation
Neutrons are electrically neutral and do not ionize directly, so they leave no direct visible track in a cloud chamber.
1678
X-rays of wavelength 3.00 Å are incident on a substance. The scattered X-rays observed at 45.0° have a different wavelength due to the Compton effect. Find the scattered wavelength:
A. 2.98 Å
B. 2.93 Å
C. 3.01 Å
D. 3.07 Å
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Correct Option
Explanation
Δλ = (2.426×10^-12 m)(1 - cos45°) ≈ 0.0071 Å, so λ' ≈ 3.007 Å ≈ 3.01 Å (option D).
1679
An α-particle is the same as
A. electromagnetic radiation of short wavelength
B. a hydrogen nucleus
C. a high speed electron
D. a helium nucleus
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Explanation
An α-particle is a helium nucleus (two protons and two neutrons).
1680
Positive rays are
A. Electrons
B. Ions
C. Neutrons
D. Electromagnetic waves
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Correct Option
Explanation
Positive rays (canal rays) consist of ions (positive charged particles), not waves, electrons, or neutrons.
