पोखरा र पूर्वाञ्चल विश्वविद्यालय PU / PoU BE प्रवेश तयारी
पोखरा र पूर्वाञ्चल विश्वविद्यालय – PU / PoU BE प्रवेश
PU BE Entrance · Pokhara & Purbanchal University BE
३,८४१ प्रश्न उपलब्ध। मोड छान्नुहोस्:
BE/B.Arch प्रवेश: 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 ray falls at 60° incidence on a glass slab 6 cm thick (n = √3). The lateral displacement of the emergent ray is about:
सही उत्तर: ग) 3.46 cm
r = 30°, and d = t sin(i − r)/cos r = 6 × sin 30°/cos 30° = 6 × 0.5/0.866 ≈ 3.46 cm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A thin prism of angle 10° has refractive indices 1.66 for violet and 1.64 for red light. The angular dispersion produced is:
सही उत्तर: ख) 0.2°
Angular dispersion = (n_v − n_r)A = 0.02 × 10° = 0.2°.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A vessel contains a 10 cm layer of oil (n = 1.5) floating on a 10 cm layer of water (n = 4/3). Viewed from directly above, the bottom appears to be at a depth of about:
सही उत्तर: ग) 14.2 cm
Apparent depth = 10/1.5 + 10/(4/3) = 6.67 + 7.5 ≈ 14.2 cm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A plano-convex lens (n = 1.5) has a curved surface of radius 30 cm. Its plane face is silvered. The system behaves like a concave mirror of focal length:
सही उत्तर: घ) 30 cm
The lens has f = R/(n − 1) = 60 cm; light passes through it twice and the plane mirror adds no power, so F = f/2 = 30 cm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A sonic boom (shock wave) is produced when:
सही उत्तर: ख) the source moves faster than the speed of sound
When the source speed exceeds the wave speed (Mach number > 1), the wavefronts pile up into a conical shock wave.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A single machine produces a sound level of 60 dB at a point. Two identical machines running together produce a level of about:
सही उत्तर: ख) 63 dB
Intensity doubles, so the level rises by 10 log₁₀2 ≈ 3 dB, giving about 63 dB.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A sonometer wire is stretched by a solid weight of relative density 8. When the weight is fully immersed in water, the fundamental frequency changes from f to about:
सही उत्तर: क) 0.94 f
Buoyancy reduces the tension to (7/8) of its value; since f ∝ √T, f′ = f√(7/8) ≈ 0.94 f.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A car approaches a large wall at 10 m/s sounding a 500 Hz horn. The frequency of the echo heard by the driver is about (speed of sound 340 m/s):
सही उत्तर: घ) 530 Hz
The wall receives f₁ = 500 × 340/330 and reflects it; the moving driver hears f₁ × 350/340 = 500 × 350/330 ≈ 530 Hz.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A stationary wave is y = 0.1 sin(πx/3) cos(40πt) in SI units. The distance between two adjacent nodes is:
सही उत्तर: ग) 3 m
k = π/3 gives λ = 2π/k = 6 m, and adjacent nodes are λ/2 = 3 m apart.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the van der Waals equation (P + a/V²)(V − b) = RT for one mole, the constant b accounts for:
सही उत्तर: क) the finite volume of the gas molecules
b is the excluded volume due to the molecules' own size; a corrects for intermolecular attraction.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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