भौतिक विज्ञान – Physics MCQ
भौतिक विज्ञान – IT प्रवेश
Physics · IT Entrance – B.Sc. CSIT, BIT & BCA · ३९५ प्रश्न
३९५ प्रश्न उपलब्ध। मोड छान्नुहोस्:
भौतिक विज्ञान: 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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The heat required to raise the temperature of 2 kg of water by 10 °C (specific heat of water = 4200 J kg⁻¹ K⁻¹) is:
सही उत्तर: ख) 84,000 J
Q = mcΔT = 2 × 4200 × 10 = 84,000 J. 42,000 J would be the answer for only 1 kg.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The SI unit of specific heat capacity is:
सही उत्तर: क) J kg⁻¹ K⁻¹
Specific heat is heat per unit mass per unit temperature change, c = Q/(mΔT), so its unit is J kg⁻¹ K⁻¹. J K⁻¹ is the unit of heat capacity of a whole body.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A temperature of 27 °C on the Kelvin scale is approximately:
सही उत्तर: घ) 300 K
T(K) = t(°C) + 273 (more precisely 273.15), so 27 °C ≈ 300 K. 246 K results from subtracting instead of adding.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The temperature at which the Celsius and Fahrenheit scales show the same reading is:
सही उत्तर: ग) −40°
Setting C = F in F = 9C/5 + 32 gives C = −40. Hence −40 °C = −40 °F.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An increase of 10 dB in sound level corresponds to an increase in intensity by a factor of:
सही उत्तर: ख) 10
Sound level β = 10 log(I/I₀) dB, so a 10 dB rise means I increases 10 times. A 20 dB rise would mean 100 times.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The fundamental frequency of an organ pipe of length L closed at one end (v = speed of sound) is:
सही उत्तर: क) v/4L
In the fundamental mode a closed pipe holds a quarter wavelength, so L = λ/4 and f = v/4L. v/2L is the fundamental of a pipe open at both ends.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An organ pipe closed at one end produces:
सही उत्तर: घ) Only odd harmonics
A closed pipe has a node at the closed end and an antinode at the open end, so only odd harmonics (f, 3f, 5f, …) are produced. An open pipe produces all harmonics.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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When a sound source moves towards a stationary listener, the frequency heard by the listener:
सही उत्तर: ग) Increases
By the Doppler effect, approach compresses the waves and raises the apparent frequency (pitch). When the source moves away the apparent frequency decreases.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A wave has frequency 500 Hz and wavelength 0.68 m. Its speed is:
सही उत्तर: क) 340 m/s
Wave speed v = fλ = 500 × 0.68 = 340 m/s. Dividing instead of multiplying gives an incorrect result.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The speed of sound in an ideal gas is proportional to (T = absolute temperature):
सही उत्तर: घ) √T
v = √(γRT/M), so v ∝ √T. This is why sound travels faster in warm air than in cold air.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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