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.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
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.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
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.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
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).
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.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
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.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
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): A vibrating tuning fork sounds louder, when its stem is pressed against a desk top.
Reason (R): When a sound wave is incident on the surface of a desk, it is totally reflected.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true due to forced vibrations and resonance. The desk provides a larger surface area to vibrate, increasing the loudness.
Reason (R) is false because sound waves are not totally reflected; some energy is transmitted to the desk.