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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Charges of +4 μC and +9 μC are 10 cm apart. The point between them where the net electric field is zero lies at a distance from the 4 μC charge of:
सही उत्तर: घ) 4 cm
k(4)/x² = k(9)/(10 − x)² gives (10 − x)/x = 3/2, so x = 4 cm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An astronomical telescope has an objective of focal length 100 cm and an eyepiece of focal length 5 cm. In normal adjustment, the length of the telescope is:
सही उत्तर: क) 105 cm
In normal adjustment the separation is f₀ + fₑ = 100 + 5 = 105 cm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Unpolarised light of intensity I₀ passes through two polarisers whose transmission axes are at 30° to each other. The intensity of the emerging light is:
सही उत्तर: ख) 3I₀/8
The first polariser gives I₀/2; Malus's law then gives (I₀/2)cos²30° = (I₀/2)(3/4) = 3I₀/8.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A short-sighted person cannot see clearly beyond 2 m. The power of the lens needed to correct this is:
सही उत्तर: ख) −0.5 D
A concave lens of focal length −2 m is needed: P = 1/f = −0.5 D.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A prism of angle 60° has an angle of minimum deviation of 60°. The refractive index of the prism is:
सही उत्तर: ग) √3
n = sin((A + δ)/2)/sin(A/2) = sin 60°/sin 30° = √3.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A plano-convex lens of glass (n = 1.5) has a curved surface of radius 30 cm. Its focal length is:
सही उत्तर: घ) 60 cm
1/f = (n − 1)(1/R) = 0.5/30, so f = 60 cm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An object is placed 10 cm in front of a convex lens of focal length 15 cm. The image is:
सही उत्तर: क) virtual, erect, 30 cm from the lens on the object's side
1/v = 1/15 − 1/10 = −1/30, so v = −30 cm: a virtual, erect image magnified 3 times on the same side as the object.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An object is placed 20 cm in front of a concave mirror of focal length 15 cm. The magnification of the image is:
सही उत्तर: क) −3
1/v = 1/f − 1/u with u = −20, f = −15 gives v = −60 cm; m = −v/u = −3 (real, inverted, three times enlarged).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A string 1 m long, fixed at both ends, has mass per unit length 0.01 kg/m and is under a tension of 100 N. Its fundamental frequency is:
सही उत्तर: ग) 50 Hz
v = √(T/μ) = √(100/0.01) = 100 m/s; f = v/2L = 50 Hz.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A source emitting 500 Hz and an observer approach each other, each moving at 10 m/s. If the speed of sound is 340 m/s, the frequency heard is about:
सही उत्तर: घ) 530 Hz
f′ = f(v + v₀)/(v − vₛ) = 500 × 350/330 ≈ 530 Hz.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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