भौतिक विज्ञान – Physics MCQ
भौतिक विज्ञान – IT प्रवेश
Physics · IT Entrance – B.Sc. CSIT, BIT & BCA · ३९५ प्रश्न
३९५ प्रश्न उपलब्ध। मोड छान्नुहोस्:
भौतिक विज्ञान: 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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The speed of light in glass of refractive index 1.5 is:
सही उत्तर: ख) 2 × 10⁸ m/s
n = c/v, so v = c/n = (3 × 10⁸)/1.5 = 2 × 10⁸ m/s. Light slows down in a denser medium, so a value larger than c is impossible.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The mode of heat transfer that does not require any material medium is:
सही उत्तर: क) Radiation
Radiation travels as electromagnetic waves and can cross vacuum, which is how the Sun's heat reaches the Earth. Conduction and convection both need a medium.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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According to Wien's displacement law, as the temperature of a black body increases, the wavelength at which its emission is maximum:
सही उत्तर: घ) Decreases
Wien's law states λ_max × T = constant, so λ_max decreases as T rises. That is why very hot bodies glow bluish-white rather than red.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the absolute temperature of a black body is doubled, the power it radiates becomes:
सही उत्तर: ग) 16 times
By the Stefan–Boltzmann law, E ∝ T⁴, so doubling T gives 2⁴ = 16 times the power. 4 times would be the case if E were proportional to T².
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For one mole of an ideal gas, Cp − Cv is equal to:
सही उत्तर: क) R
Mayer's relation gives Cp − Cv = R for molar specific heats. Cp is larger because at constant pressure some heat goes into doing work during expansion.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The first law of thermodynamics is a statement of the conservation of:
सही उत्तर: घ) Energy
The first law, ΔQ = ΔU + ΔW, says heat supplied goes into internal energy and work, which is conservation of energy. Entropy is not conserved; the second law deals with it.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An adiabatic process is one in which:
सही उत्तर: ख) No heat is exchanged with the surroundings
In an adiabatic process Q = 0, so any work done changes the internal energy. Constant temperature defines an isothermal process instead.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In an isothermal process of an ideal gas, the change in internal energy is:
सही उत्तर: क) Zero
The internal energy of an ideal gas depends only on temperature, which stays constant, so ΔU = 0. Then all heat supplied is converted into work (Q = W).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the absolute temperature of a gas is made four times, the rms speed of its molecules becomes:
सही उत्तर: घ) Two times
v_rms = √(3RT/M), so v_rms ∝ √T. Four times the temperature gives √4 = 2 times the rms speed.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The law stating that the volume of a fixed mass of gas is directly proportional to its absolute temperature at constant pressure is:
सही उत्तर: ग) Charles's law
Charles's law: V ∝ T at constant pressure. Boyle's law relates pressure and volume at constant temperature.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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