भौतिक विज्ञान (Physics) – Physics MCQ
भौतिक विज्ञान (Physics) – इन्जिनियरिङ प्रवेश
Physics · Engineering Entrance – Mathematics, Physics, Chemistry & English · १,३९८ प्रश्न
१,३९८ प्रश्न उपलब्ध। मोड छान्नुहोस्:
भौतिक विज्ञान (Physics): प्रश्न र उत्तर
सही लागेको विकल्पमा थिच्नुहोस्। सही भए हरियो, गलत भए रातो देखिन्छ; ३ सेकेन्डपछि सही उत्तर र व्याख्या देखिन्छ।
सही: ० / ०
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A very high temperature is required for nuclear fusion in order to:
सही उत्तर: क) give nuclei enough energy to overcome their Coulomb repulsion
Light nuclei must come within the range of nuclear forces, which requires overcoming the electrostatic barrier.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a nuclear reactor, cadmium or boron rods are used to:
सही उत्तर: ख) absorb neutrons and control the chain reaction
Cadmium and boron have large neutron-absorption cross-sections; inserting the rods reduces the neutron population.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Nuclear forces are:
सही उत्तर: ख) short-ranged and nearly charge-independent
The strong nuclear force acts over about 1–3 fm and acts similarly between n–n, p–p and n–p pairs.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Nuclei having the same mass number but different atomic numbers are called:
सही उत्तर: ग) isobars
Isobars (e.g. ⁴⁰Ar and ⁴⁰Ca) have the same A but different Z.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The fraction of radioactive nuclei remaining undecayed after a time equal to two mean lives is about:
सही उत्तर: घ) 13.5%
N/N₀ = e^(−t/τ) = e⁻² ≈ 0.135.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the Bohr model of hydrogen, the frequency of revolution of the electron in the n-th orbit is proportional to:
सही उत्तर: क) 1/n³
f = v/(2πr) with v ∝ 1/n and r ∝ n², so f ∝ 1/n³.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The kinetic energy of the electron in the ground state of a hydrogen atom is:
सही उत्तर: क) 13.6 eV
In the Bohr model KE = −E = +13.6 eV and PE = 2E = −27.2 eV for the ground state.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The Paschen series of the hydrogen spectrum lies in the:
सही उत्तर: ख) infrared region
Paschen lines arise from transitions to n = 3 and have wavelengths in the infrared.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The Compton effect provides evidence for:
सही उत्तर: ग) the particle (photon) nature of radiation
The wavelength shift of X-rays scattered by electrons is explained by treating photons as particles carrying momentum.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A series LCR circuit driven at a frequency below its resonant frequency behaves as:
सही उत्तर: घ) a capacitive circuit (current leads voltage)
Below resonance X_C = 1/(ωC) exceeds X_L = ωL, so the net reactance is capacitive.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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