पोखरा र पूर्वाञ्चल विश्वविद्यालय PU / PoU BE प्रवेश तयारी
पोखरा र पूर्वाञ्चल विश्वविद्यालय – PU / PoU BE प्रवेश
PU BE Entrance · Pokhara & Purbanchal University BE
३,८३७ 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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When a dielectric slab of dielectric constant K completely fills the space between the plates of a parallel-plate capacitor, its capacitance:
सही उत्तर: ख) Becomes K times
C = Kε₀A/d, so capacitance increases K times. For an isolated charged capacitor, the potential difference then decreases by K.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The electric field inside a charged hollow conducting sphere is:
सही उत्तर: क) Zero
All charge resides on the outer surface, and by Gauss's law the enclosed charge is zero, so E = 0 inside. The potential inside, however, is constant and non-zero.
💬 टिप्पणी / गल्ती रिपोर्ट (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)
यी अभ्यास प्रश्न हुन्, आधिकारिक प्रश्न होइनन्। पाठ्यक्रम, विज्ञापन र नतिजाका लागि सम्बन्धित निकायको आधिकारिक वेबसाइट हेर्नुहोस्। उत्तरमा गल्ती भेटे प्रश्नमुनिको "टिप्पणी / गल्ती रिपोर्ट" मा लेख्नुहोस्।
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