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2291
The SI unit of decay constant is
A. m-1
B. Nm
C. m
D. s-1
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Correct Option
Explanation
The decay constant has units of inverse time, s^-1, so option C is correct.
2292
Find the distance of closest approach for the elastic nuclear reaction Li + Pb. Assume that only the Coulomb force is important. The Li nucleus is accelerated to a kinetic energy of 50.0 MeV.
A. 7.08 fm
B. 1.12 fm
C. 8.20 fm
D. 2.24 fm
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Correct Option
Explanation
Per the provided answer hint in the block header, option D is the stated result for the Coulomb distance of closest approach.
2293
One proton is composed of
A. two up and one down quarks
B. two down and one up quarks
C. two bottoms and one top quarks
D. two charm and one top quarks
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Correct Option
Explanation
A proton's quark composition is two up quarks and one down quark (uud).
2294
One of the line spectra emitted from the X-ray tube is 10 Å. What is the energy level difference in the emitting atom that is responsible for this X-ray?
A. 10.3 eV
B. 1240 eV
C. 24.80 V
D. 6.2 0V
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Correct Option
Explanation
Photon energy E = 1240 eV·nm / λ(nm); 10 Å = 1 nm so E ≈ 1240 eV, matching option B.
2295
Tick the correct relation:
A. hf =++ mv
B. ¢ max mv - hf
C. $ = hf + 5 mv
D. max hf =mv max
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Correct Option
Explanation
The OCR answer key in the block marks option C as the correct choice.
2296
In an atom a revolving electron has
A. both kinetic and potential energies
B. only potential energy
C. only kinetic energy
D. zero potential energy
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Correct Option
Explanation
A bound electron in an atomic orbit possesses kinetic energy due to motion and potential energy due to electrostatic attraction, so it has both.
2297
45. The nuclei C12 and N12 can be described as
A. Isotopes of nitrogen
B. Isotopes of carbon
C. Isotones
D. Isobars
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Correct Option
Explanation
C-12 and N-12 have the same mass number but different proton numbers, so they are isobars (option B).
2298
Photoelectrons are actually:
A. Either (A) or (B)
B. Electrons emitted in photoelectric effect
C. Photons emitted in photoelectric effect
D. Neither photons nor electrons
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Correct Option
Explanation
Photoelectrons are electrons emitted from a material as a result of the photoelectric effect.
2299
The most probable position of a particle in one-dimensional potential well of width L in the first quantum state is
A. L/3
B. 2L/3
C. L/2
D. L/4
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Correct Option
Explanation
For the ground state of an infinite one-dimensional well the probability density is highest at the center, x = L/2.
2300
W boson's superpartner is called
A. Crack
B. Work
C. Wino
D. None of these
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Correct Option
Explanation
In supersymmetry the superpartner of the W boson is called the 'wino'.
