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The MCQs below are drawn from the Physics subject category.
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2491
In the photoelectric effect, the threshold wavelength is 2756 Å. If light of wavelength 1700 Å is incident on a metal substance, determine the kinetic energy of the photoelectrons:
A. 7.29 eV
B. 2.79 eV
C. 4.50 eV
D. 2.25 eV
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Correct Option
Explanation
The block header provides the answer key indicating option A; the OCR answer key is used as the source per the block metadata.
2492
In the photoelectric effect, electromagnetic radiation is incident upon the surface of a metal. Which of the following is not a true statement about the photoelectric effect?
A. Above the threshold frequency, the flux of electrons per second increases as the intensity of incident light.
B. The stopping potential V_s is proportional to ν^2.
C. There is no photocurrent unless ν > ν_threshold.
D. ν_threshold is characteristic of the cathode material.
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Correct Option
Explanation
The block header marks option D as the incorrect statement; the stopping potential is proportional to photon frequency (linearly) not to the square of frequency, so D is false.
2493
In demonstrating photoelectric effect, when light falling on the cathode is cut off, the ammeter shows:
A. No mesons passing through it
B. No photons passing through it
C. Maximum number of electrons passing through it
D. No electrons passing through it
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Correct Option
Explanation
When the incident light is removed, photoelectrons are no longer emitted so the current (electrons) measured by the ammeter drops to zero.
2494
In photoelectric effect removal of photons is observed at ____ energies.
A. Low.
B. High.
C. Intermediate.
D. Both A and C.
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Correct Option
Explanation
The OCR indicates option D is selected; the block text shows a selection mark adjacent to 'Both A and C.'
2495
Which experiment confirmed the de Broglie hypothesis?
A. Schrodinger's Cat experiment
B. Bohr's experiment
C. Davison-Germer experiment
D. Double-slit experiment
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Correct Option
Explanation
The Davison-Germer experiment showed electron diffraction consistent with de Broglie's matter waves, confirming his hypothesis.
2496
If positive terminal of the battery is connected to n-type and negative terminal of the battery is connected to p-type, then the diode is
A. forward biased
B. a gate
C. reverse biased
D. saturated
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Correct Option
Explanation
Connecting positive to n-type and negative to p-type widens the depletion region, placing the diode in reverse bias.
2497
No deflection in the galvanometer in a balanced wheat-stone bridge means that the terminals of galvanometer are at:
A. Same potential
B. Different potentials
C. Zero potential
D. Both (A) and (C)
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Correct Option
Explanation
Zero deflection indicates no potential difference between the galvanometer terminals, i.e., they are at the same potential.
2498
212 Conductance is the reciprocal of
A. admittance
B. inductance
C. capacitance
D. resistance
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Correct Option
Explanation
Conductance G is defined as the reciprocal of resistance R (G = 1/R).
2499
338. Ohm's law is not obeyed by
A. electrolytes
B. discharge tube
C. vacuum tubes
D. all of these
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Correct Option
Explanation
Non-ohmic devices such as electrolytes, discharge tubes, and vacuum tubes do not have a linear V–I relationship, so all listed options are correct.
2500
16. At resonance the value of power factor in an L.C.R series circuit is:
A. One
B. /2
C. Zero
D. Infinite
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Correct Option
Explanation
At resonance in a series LCR circuit the voltage and current are in phase, giving a power factor of 1, so option D is correct.
