An echo returned in 0.5 s. If speed of sound is 340 m/s, the distance of reflecting surface is MCQ with Answer and Explanation
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Question #1
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Simple harmonic motion is characterized by:
Correct Answer: Option C
Explanation:
SHM definition: acceleration a ∝ -x (displacement), i.e., a = -ω²x. This restoring acceleration causes oscillatory motion. Constant acceleration implies uniformly accelerated motion (not oscillatory). Constant velocity implies no acceleration. Memory tip: 'SHM: a = -ω²x; force F = -kx (Hooke's law)'. This conceptual question tests fundamental SHM characteristics, frequently examined in competitive exams. Always link to examples: mass-spring system, simple pendulum (small angles), LC circuits.
SHM definition: acceleration a ∝ -x (displacement), i.e., a = -ω²x. This restoring acceleration causes oscillatory motion. Constant acceleration implies uniformly accelerated motion (not oscillatory). Constant velocity implies no acceleration. Memory tip: 'SHM: a = -ω²x; force F = -kx (Hooke's law)'. This conceptual question tests fundamental SHM characteristics, frequently examined in competitive exams. Always link to examples: mass-spring system, simple pendulum (small angles), LC circuits.
Question #2
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When a source of sound moves towards a stationary observer, the apparent frequency:
Correct Answer: Option D
Explanation:
This is the Doppler effect: when source moves toward observer, wavefronts compress, decreasing wavelength, thus increasing apparent frequency (f' = f·v/(v - v_s), where v is sound speed, v_s source speed). Conversely, receding source decreases frequency. This applies to all waves (light, sound). Memory aid: 'Approaching = higher pitch (frequency); Receding = lower pitch'. Competitive exams often test qualitative understanding before formula application. Always identify motion direction relative to observer for sign conventions in numerical problems.
This is the Doppler effect: when source moves toward observer, wavefronts compress, decreasing wavelength, thus increasing apparent frequency (f' = f·v/(v - v_s), where v is sound speed, v_s source speed). Conversely, receding source decreases frequency. This applies to all waves (light, sound). Memory aid: 'Approaching = higher pitch (frequency); Receding = lower pitch'. Competitive exams often test qualitative understanding before formula application. Always identify motion direction relative to observer for sign conventions in numerical problems.
Question #3
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Which defect of vision is correctly matched with its correcting lens?
Correct Answer: Option B
Explanation:
Myopia (near-sightedness) occurs when the image is focused in front of the retina. It is corrected using a concave (diverging) lens. Hypermetropia (far-sightedness) is corrected with a convex (converging) lens. Astigmatism is corrected with a cylindrical lens. Presbyopia is usually corrected with bifocal lenses.
Myopia (near-sightedness) occurs when the image is focused in front of the retina. It is corrected using a concave (diverging) lens. Hypermetropia (far-sightedness) is corrected with a convex (converging) lens. Astigmatism is corrected with a cylindrical lens. Presbyopia is usually corrected with bifocal lenses.
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