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 spectral line from a distant galaxy is observed with its wavelength increased by 0.1%. The galaxy is receding at about:
सही उत्तर: घ) 300 km/s
For v ≪ c, Δλ/λ = v/c, so v = 0.001 × 3 × 10⁸ m/s = 3 × 10⁵ m/s = 300 km/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In Young's experiment, light of wavelengths 600 nm and 400 nm is used together. The first point beyond the centre where bright fringes of both coincide corresponds to:
सही उत्तर: क) the 2nd bright fringe of 600 nm and the 3rd of 400 nm
Coincidence needs n₁ × 600 = n₂ × 400; the smallest solution is n₁ = 2, n₂ = 3 (path difference 1200 nm).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A thin film of refractive index 1.5 in air is illuminated normally with light of wavelength 600 nm. The minimum thickness for which the reflected light is strongly reinforced is:
सही उत्तर: ग) 100 nm
With a phase reversal at the top surface only, reflection maxima need 2nt = (m + ½)λ; the least thickness is λ/(4n) = 600/6 = 100 nm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The limit of resolution of the normal human eye is about:
सही उत्तर: ख) 1 minute of arc
Two points can be resolved by the eye if they subtend about 1′ (≈ 3 × 10⁻⁴ rad) or more.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A primary rainbow is seen at an angle of about how much from the antisolar point (the direction opposite the Sun)?
सही उत्तर: घ) 42°
Light refracted, reflected once inside drops and refracted again is concentrated near 42° (red outside, violet inside); the secondary bow is near 51°.
💬 टिप्पणी / गल्ती रिपोर्ट (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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