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 coin at the bottom of a 12 cm deep tank of water (refractive index 4/3) appears raised. Its apparent depth when viewed from above is:
सही उत्तर: घ) 9 cm
Apparent depth = real depth / n = 12/(4/3) = 9 cm. 3 cm is the apparent rise (normal shift), not the apparent depth.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two coherent light waves meet with a path difference of λ/2. The result at that point is:
सही उत्तर: ग) Destructive interference (dark)
A path difference of λ/2 corresponds to a phase difference of π, so the waves cancel. Constructive interference needs a path difference of nλ.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The polarizing (Brewster's) angle for a glass of refractive index √3 is:
सही उत्तर: ख) 60°
Brewster's law: tan θp = n = √3, so θp = 60°. At this angle the reflected and refracted rays are perpendicular.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The phenomenon of polarization shows that light waves are:
सही उत्तर: क) Transverse
Only transverse waves can be polarized because their vibrations can be restricted to one plane. Sound waves in air, being longitudinal, cannot be polarized.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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When white light passes through a glass prism, the colour deviated the most is:
सही उत्तर: घ) Violet
Glass has the highest refractive index for violet light (shortest wavelength among visible colours), so it deviates most. Red deviates the least.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The blue colour of the clear sky is mainly due to:
सही उत्तर: ग) Scattering of light
Rayleigh scattering is proportional to 1/λ⁴, so shorter (blue) wavelengths are scattered much more by air molecules. Dispersion explains the rainbow, not the blue sky.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Two thin convex lenses each of focal length 20 cm are placed in contact. The focal length of the combination is:
सही उत्तर: ख) 10 cm
1/F = 1/20 + 1/20 = 1/10, so F = 10 cm. Powers add in contact, so the combination is stronger and has a shorter focal length.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Total internal reflection can occur when light travels:
सही उत्तर: घ) From a denser to a rarer medium at an angle of incidence greater than the critical angle
Both conditions are needed: denser to rarer medium and angle of incidence exceeding the critical angle. Optical fibres work on this principle.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The speed of light in a glass of refractive index 1.5 is:
सही उत्तर: ग) 2 × 10⁸ m/s
v = c/n = 3 × 10⁸ / 1.5 = 2 × 10⁸ m/s. Light is slower in an optically denser medium, so it can never exceed 3 × 10⁸ m/s.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the intensity of a sound is increased by a factor of 10, the sound level increases by:
सही उत्तर: ख) 10 dB
β = 10 log₁₀(I/I₀); multiplying I by 10 adds 10 log₁₀10 = 10 dB. 20 dB corresponds to a 100-fold increase in intensity.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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