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The MCQs below are drawn from the Physics subject category.
Showing 1611–1620
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1611
A radioactive substance has a half life of four months. Three-fourths of the substance will decay in
A. Eight months
B. Twelve months
C. Three months
D. Four months
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Correct Option
Explanation
If three-fourths decay, one-quarter remains = (1/2)^n => n = 2 half-lives; time = 2 * 4 months = 8 months.
1612
In a cloud chamber the path of beta-particles is:
A. Thin, straight, short
B. Thin, wavy, shorter
C. Straight, thick, short
D. Thin, wavy, longer
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Correct Option
Explanation
The OCR indicates option C (thin, wavy, longer) as the selected answer; beta particles produce thin, often wavy and longer tracks than alpha particles.
1613
From which radiation it is most difficult to protect oneself?
A. ß-radiation
B. y-radiation
C. a-radiation
D. Heat radiation
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Correct Option
Explanation
Gamma (γ) radiation is highly penetrating and hardest to shield against, so option C is correct.
1614
53. Fission is induced in U235 by
A. Electrons
B. α particles
C. Neutrons
D. Protons
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Correct Option
Explanation
Neutrons commonly induce fission in U-235, making option C correct.
1615
The idea of quantization of energy was proposed by:
A. Max. Planck
B. Maxwell
C. Bohr
D. Einstein
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Correct Option
Explanation
Max Planck introduced energy quantization in his blackbody radiation work, proposing energy quanta E = hf.
1616
Which of the following wavelengths lies in X-ray region?
A. 100 Å
B. 1 Å
C. 1,000 Å
D. 10,000 Å
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Correct Option
Explanation
X-ray wavelengths are on the order of 1 Å (10^-10 m), so option A is in the X-ray region.
1617
When we pass a radiation from a radioactive material through an electric field
A. only the α-particles are deflected
B. all three kinds of rays will be deflected
C. the α and β-particles are deflected
D. only the γ-rays are deflected
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Correct Option
Explanation
Alpha and beta particles are charged and are deflected by electric fields, while gamma rays are uncharged and are not deflected.
1618
Which one of the following emission takes place in a nuclear reaction?
A. Gamma
B. Photons
C. Alpha
D. Beta
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Correct Option
Explanation
The OCR header hint indicates option C (beta) is the keyed answer for this nuclear reaction emission question.
1619
The electron kinetic energy that corresponds to a momentum of 1.1 x 10^{-20} kg-m/sec is:
A. 21 MeV
B. 17 MeV
C. 18 MeV
D. 20 MeV
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Correct Option
Explanation
The block provides answer hint A; the OCR answer key indicates 17 MeV as the listed correct choice.
1620
63. First machine which achieved 1.5 MeV energy to accelerate charged particles was:
A. Van De Graaf machine
B. Cockcroft-Walton machine
C. Cyclotron
D. Linear Accelerator
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Correct Option
Explanation
Van de Graaff electrostatic generators are known for achieving megavolt-class accelerating voltages (≈1.5 MeV), so Van De Graaf machine is the appropriate choice.
