Sound Wave and its Characteristics - NEET Physics Chapterwise MCQs & PYQs
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NEET Sound Wave and its Characteristics MCQs & PYQs
Practice NEET Sound Wave and its Characteristics Questions
Question 11:
easy
Assertion (A): When two vibrating tuning forks having frequencies \(240 \text{ Hz}\) and \(300 \text{ Hz}\) are held near each other, beats cannot be heard by us.
Reason (R): This is because beats cannot be distinctly heard due to the property of persistence of hearing.
The beat frequency is \(|240 - 300| = 60 text{ Hz}\) . For distinct beats to be heard, the beat frequency should be less than \(10 text{ Hz}\) . Thus, Assertion (A) is true. Persistence of hearing is not the reason for inability to hear distinct beats; it's the ear's inability to follow rapid amplitude changes. Thus, Reason (R) is false.
Assertion (A): When two tuning fork of frequency \(256 \text{ Hz}\) and \(324 \text{ Hz}\) are vibrating together. Beats will not be heard.
Reason (R): Superposition of sound waves is possible for all frequencies of sound.
The beat frequency is \(|256 - 324| = 68 \text{ Hz}\) . Since this is much greater than \(10 \text{ Hz}\) , distinct beats cannot be heard. Thus, (A) is true. The principle of superposition holds for all sound waves irrespective of their frequency, so (R) is true. However, (R) does not explain (A).
Assertion (A): Sound waves travel faster on a hot summer day than on a cold winter day.
Reason (R): Velocity of sound is directly proportional to the temperature of medium.
Sound speed increases with temperature. A summer day is hotter than a winter day, so sound travels faster. Assertion (A) is true. The velocity of sound in a gas is proportional to the square root of the absolute temperature (\(v \propto \sqrt{T}\)), not directly proportional. So, Reason (R) is false.
Assertion (A): Beats are not observed in case of light waves from two independent sources.
Reason (R): The phase difference between two light sources changes randomly.
Stable beats require coherent sources with a constant phase difference. Independent light sources have rapidly and randomly changing phase differences, making stable beats unobservable.
Thus, Assertion (A) is true, and Reason (R) is true and is the correct explanation of (A).
Assertion (A): When we start filling an empty bucket with water, the pitch of sound produced goes on decreasing.
Reason (R): The frequency of man voice is usually higher than that of woman.
As water fills a bucket, the air column length decreases, increasing the resonant frequency and thus the pitch. So, Assertion (A) is false. The average frequency of a man's voice is lower than a woman's voice. So, Reason (R) is also false.
Assertion (A): Sound is produced due to vibratory motion, but a vibrating pendulum does not produce audible sound.
Reason (R): A vibrating source always produce audible sound.
Sound is produced by vibrations. A vibrating pendulum's frequency is typically below the audible range (infrasound), so it does not produce audible sound. Thus, Assertion (A) is true.
Reason (R) is false because a vibrating source must have a frequency within 20 Hz to 20 kHz to produce audible sound.
Assertion (A): With increase in temperature, the speed of sound in a gas increases.
Reason (R): When temperature increases, the gas molecules move faster.
The speed of sound in a gas is \(v = \sqrt{\frac{\gamma RT}{M}}\), so it increases with temperature. Thus, Assertion (A) is true. Higher temperature means gas molecules move faster, leading to quicker sound transmission. So, Reason (R) is true and explains (A).