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 proton and a deuteron with equal kinetic energies enter a uniform magnetic field perpendicular to it. The ratio of the radii of their circular paths (proton : deuteron) is:
सही उत्तर: ग) 1 : √2
r = mv/(qB) = √(2mK)/(qB); both have charge e and the deuteron has twice the mass, so r_p : r_d = 1 : √2.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Point charges +4 μC and −1 μC are placed 1 m apart. On the line joining them, the electric field is zero at a point:
सही उत्तर: घ) 1 m from the −1 μC charge, on the side away from +4 μC
Between unlike charges the fields add, so the null point is outside, nearer the smaller charge: 4/(x + 1)² = 1/x² gives x = 1 m beyond the −1 μC charge.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two pipes have the same length: one open at both ends and one closed at one end. The ratio of the frequency of the second harmonic of the open pipe to the fundamental frequency of the closed pipe is:
सही उत्तर: क) 4 : 1
Open pipe: fₙ = nv/(2L), so f₂ = v/L; closed pipe: f₁ = v/(4L). Ratio = (v/L)/(v/4L) = 4.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An air bubble rising from the bottom of a lake doubles its volume on reaching the surface (temperature constant). If atmospheric pressure equals the pressure of a 10 m column of water, the depth of the lake is:
सही उत्तर: ख) 10 m
Boyle's law: (H + h)V = H(2V) with H = 10 m of water, so H + h = 2H and h = 10 m.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A particle in SHM has speed 4 cm/s at displacement 3 cm and speed 3 cm/s at displacement 4 cm. Its amplitude is:
सही उत्तर: क) 5 cm
v² = ω²(A² − x²): 16 = ω²(A² − 9) and 9 = ω²(A² − 16). Subtracting, 7 = 7ω², so ω = 1 rad/s and A² = 9 + 16 = 25, A = 5 cm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a photoelectric experiment, the frequency of the incident light is increased by 2.42 × 10¹⁴ Hz. The stopping potential increases by about (h = 6.63 × 10⁻³⁴ J s, e = 1.6 × 10⁻¹⁹ C):
सही उत्तर: ख) 1.0 V
eV₀ = hν − φ, so ΔV₀ = hΔν/e = (6.63 × 10⁻³⁴ × 2.42 × 10¹⁴)/(1.6 × 10⁻¹⁹) ≈ 1.0 V.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Light travels from glass (n = 3/2) towards water (n = 4/3). The critical angle C for the glass–water boundary is given by:
सही उत्तर: ग) sin C = 8/9
sin C = n_rarer/n_denser = (4/3)/(3/2) = 8/9, so C ≈ 62.7°.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A wire is stretched so that its length increases by 1% while its volume stays constant. Its resistance increases by about:
सही उत्तर: घ) 2%
With volume constant, A ∝ 1/L, so R = ρL/A ∝ L²; R'/R = (1.01)² ≈ 1.02, an increase of about 2%.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 0.1 kg ball is projected at 20 m/s at 30° to the horizontal. Its angular momentum about the point of projection when it is at the highest point is about (g = 10 m/s²):
सही उत्तर: घ) 8.7 kg m²/s
At the top H = u² sin²θ/(2g) = 5 m and the velocity is horizontal, u cos θ = 17.32 m/s, so L = m(u cos θ)H = 0.1 × 17.32 × 5 ≈ 8.7 kg m²/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Gamma rays originate from:
सही उत्तर: ग) transitions between energy levels of the nucleus
γ rays are emitted when an excited nucleus drops to a lower nuclear energy level.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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