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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By Rayleigh's law, the intensity of light scattered by small particles varies as 1/λ⁴. Light of 400 nm is therefore scattered more than light of 800 nm by a factor of:
सही उत्तर: घ) 16
Ratio = (800/400)⁴ = 2⁴ = 16.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Chromatic aberration is not produced by a spherical mirror because:
सही उत्तर: क) the law of reflection does not depend on wavelength
Reflection angles are the same for all colours, so all wavelengths focus at the same point; chromatic aberration arises from dispersion in refraction.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A concave mirror forms a virtual, erect and magnified image when the object is placed:
सही उत्तर: ग) between the pole and the focus
Only for an object within the focal length does a concave mirror give a virtual, upright, enlarged image (used as a shaving mirror).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two plane mirrors are placed parallel to each other, facing each other, with an object between them. The number of images formed is:
सही उत्तर: क) infinite
n = 360°/θ − 1 becomes infinite as θ → 0; repeated reflections between parallel mirrors give an endless series of images.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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For refraction at a single spherical surface of radius R separating media of refractive indices n₁ (object side) and n₂, the relation between object distance u and image distance v is:
सही उत्तर: घ) n₂/v − n₁/u = (n₂ − n₁)/R
This is the standard formula for refraction at a spherical surface (with the Cartesian sign convention); the lens-maker's formula follows by applying it twice.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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When a wave on a string is reflected from a rigidly fixed end, the reflected wave undergoes a phase change of:
सही उत्तर: क) π
A fixed end must be a node, so the reflected wave is inverted, i.e. phase change of π.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The wave y = A sin(ωt + kx) travels:
सही उत्तर: क) along the negative x-direction
The phase ωt + kx stays constant when x decreases as t increases, so the wave moves towards −x with speed ω/k.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A source of sound and an observer move in the same direction with the same speed through still air. The frequency heard by the observer is:
सही उत्तर: ग) the same as the source frequency
With v_s = v_o in the same direction, f′ = f(v − v_o)/(v − v_s) = f; there is no relative motion and no Doppler shift.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The speed of longitudinal waves in a steel rod with Young's modulus 2 × 10¹¹ N/m² and density 8000 kg/m³ is:
सही उत्तर: ख) 5000 m/s
v = √(Y/ρ) = √(2 × 10¹¹/8000) = √(2.5 × 10⁷) = 5000 m/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Relative humidity of air is defined as the ratio of:
सही उत्तर: क) the actual vapour pressure to the saturated vapour pressure at the same temperature
RH = (actual vapour pressure/SVP at that temperature) × 100%; it equals 100% when the air is saturated.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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