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The MCQs below are drawn from the Physics subject category.
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2221
The Q" hyperon has rest mass of:
A. 3,290 m. V
B. 3,293 mc
C. 3,292 m.
D. 3,291 me
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Correct Option
Explanation
The OCR answer hint marks option A (3,290 m. V) as the rest mass value for the Q" hyperon shown in the text.
2222
Fission is induced in U-235 by
A. Electrons
B. Protons
C. alpha particles
D. Neutrons
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Correct Option
Explanation
Induced fission of U-235 occurs when it absorbs a neutron, making option C correct.
2223
The net magnetic field created by the electrons within an atom is due to the field created by their ____ motion.
A. Orbital × spin.
B. Orbital.
C. Orbital & spin.
D. Spin.
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Correct Option
Explanation
Both orbital motion and intrinsic spin of electrons contribute to the magnetic moment and net magnetic field of an atom.
2224
A freshly prepared radioactive source of half life 2 hrs emits radiations of intensity which is 64 times the permissible safe level. The minimum time after which it would be possible to work safely with this source is
A. 12 hrs
B. 128 hrs
C. 6 hrs
D. 24 hrs
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Correct Option
Explanation
A reduction by factor 64 requires 6 half-lives (1/64 = (1/2)^6); with half-life 2 hrs, time = 6 * 2 = 12 hrs.
2225
The meson theory of nuclear forces suggests a nucleon potential of the form U(r) = V_R e^{-K_R r}/r - V_A e^{-K_A r}/r. Determine the form of the repulsive part of the force, the so-called hard core.
A. (V_i e^{-K_A r}/r) [K_A + 1/r]
B. V_A K_A e^{-K_A r}/r
C. V_R K_R e^{-K_R r}/r
D. (V_R e^{-K_R r}/r) [K_R + 1/r]
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Correct Option
Explanation
The repulsive (short-range) Yukawa term leads to a force proportional to V_R K_R e^{-K_R r}/r, corresponding to option C.
2226
If an object moves with velocity of light, the relative velocity will be
A. zero
B. c
C. c/2
D. infinity
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Correct Option
Explanation
The speed of light is invariant in relativity, so the relative speed of light is c.
2227
The half-life period of a radioactive substance is 5 min. The amount of substance decayed in 20 min will be:
A. 93.75%
B. 75%
C. 25%
D. 6.25%
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Correct Option
Explanation
20 min = 4 half-lives so remaining fraction = (1/2)^4 = 1/16 = 6.25%, hence decayed = 100% - 6.25% = 93.75%.
2228
Pions and Kaons belong to the ____ type of subatomic elements.
A. Electrons
B. Mesons
C. Neutrons
D. None of these
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Correct Option
Explanation
Pions and kaons are mesons, a class of hadronic subatomic particles composed of a quark and an antiquark.
2229
In an expression for time dilation, the quantity 1 - v^2/c^2 is always
A. greater than zero
B. less than one
C. equal to zero
D. equal to one
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Correct Option
Explanation
For 0 < v < c, 1 - v^2/c^2 is a positive number less than one, so option D is correct.
2230
Which of the following property must be there in a substance so that it can be used as target in X-ray tube?
A. It must have low melting point
B. It must have high reflecting ability
C. It must have high atomic number
D. It must have low atomic number
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Correct Option
Explanation
Target materials for X-ray tubes are chosen with high atomic number to increase X-ray production efficiency and characteristic X-ray yield.
