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The MCQs below are drawn from the Physics subject category.
Showing 1691–1700
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1691
Which of the quantity is dimensionless?
A. Work
B. Stress
C. Modulus of elasticity
D. Strain
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Correct Option
Explanation
Strain is a ratio of length change to original length and thus has no units, making it dimensionless.
1692
Use your knowledge of nuclear and particle physics to determine which elementary cross-section the below curve represents. σ(mb) vs. GeV (figure shown).
A. The nn elastic cross-section
B. The νn cross-section
C. The pp total cross-section
D. The direct pn cross-section
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Correct Option
Explanation
The question's answer hint in the block header indicates option A as the correct identification of the plotted total cross-section.
1693
X-rays are used for
A. detecting flaws in welding and casting
B. retina stitching in eye operations
C. detecting heavy elements under the earth
D. cutting, boring and precision welding
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Correct Option
Explanation
X-rays are commonly used in non-destructive testing to detect flaws in welds and castings.
1694
Which of the following is required for maintaining sustained chain reaction?
A. Photons
B. Neutrons
C. Electrons
D. Protons
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Correct Option
Explanation
A sustained chain reaction depends on free neutrons causing further fissions.
1695
A freshly made sample of radioactive material gives a count rate of 8,000 counts per minute. After twenty days, it gives a count rate of 500 counts per minute. What is the half-life of the material?
A. 10 days
B. 5 days
C. 20 days
D. 40 days
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Correct Option
Explanation
8000 → 500 is a factor of 16 decrease, i.e., 4 half-lives in 20 days, so half-life = 20/4 = 5 days (option A).
1696
In radiotherapy, X-rays are used to
A. treat cancer
B. detect bone fracture
C. cure heart disease
D. all of the above
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Correct Option
Explanation
Radiotherapy uses high-energy X-rays to destroy or damage cancerous cells, so 'treat cancer' is correct.
1697
Beta ray emitted by a radioactive substance is:
A. An electron which was existing outside the nucleus
B. A pulse of electromagnetic wave
C. An electron emitted by the nucleus as a result of the decay of neutron inside the nucleus
D. An electron which was existing inside the nucleus
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Correct Option
Explanation
Beta decay involves a neutron converting to a proton and emitting an electron (beta particle) from the nucleus.
1698
The total energy of an atomic electron is:
A. Less than zero
B. Zero
C. More than zero
D. All of these
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Correct Option
Explanation
Bound atomic electrons have negative total energy (less than zero), as indicated by the provided answer key.
1699
At high temperature, a body generally emits radiations of
A. moderate wavelengths
B. small wavelengths
C. zero wavelengths
D. long wavelengths
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Correct Option
Explanation
Higher temperature shifts blackbody emission toward shorter (smaller) wavelengths, so high temperature corresponds to small wavelengths.
1700
When 3d subshell is complete, the newly entering electron goes into
A. 5s
B. 4d
C. 4p
D. 4s
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Correct Option
Explanation
After completion of 3d, the next available higher-energy orbital according to the Aufbau order is 4p.
