Assertion (A): When a high pressure pulse of air travelling down an open pipe reaches the other end, turns into a pulse of low pressure pulse travelling up the tube.
Reason (R): Node of pressure means antinode of displacement in case of open pipe.
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
At an open end, the pressure must remain atmospheric, establishing a pressure node. An incident high pressure pulse reflects as a low pressure pulse ((pi) phase change) to maintain this. Thus (A) is true. At a pressure node, particles have maximum displacement, which is a displacement antinode. Thus (R) is true and explains the reflection in (A).
Assertion (A): A person hear maximum sound at displacement node.
Reason (R): Pressure change is maximum at displacement node.
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
Our ears perceive sound based on pressure variations. At a displacement node, particles have zero displacement, but pressure variations are maximum (a pressure antinode). Therefore, maximum sound is heard at a displacement node. Both (A) and (R) are true, and (R) provides the direct physical reason for (A).
Assertion (A): In a hoop revolving with some angular speed \(\omega\) in horizontal plane, transverse wave may appear to be stationary.
Reason (R): Velocity of transverse wave pulse w.r.t. string may be equal and opposite to string velocity.
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. If a transverse wave pulse propagates along the rotating hoop in a direction opposite to the hoop's rotation, and its speed relative to the string is equal to the string's linear speed, the wave appears stationary to a ground observer. Reason (R) provides this exact condition: if \(v_{\text{wave relative to string}} = -v_{\text{string}}\), then the net velocity relative to the lab frame is zero. Both are true and (R) correctly explains (A).
Assertion (A): In longitudinal wave propagation the distance between two consecutive compression is equal to wavelength of wave.
Reason (R): Standing wave is not a wave as it does not transport energy.
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 by definition. Wavelength (\(lambda\)) in a longitudinal wave is the distance between two consecutive compressions or rarefactions. Reason (R) is false; a standing wave is a form of wave resulting from the superposition of two progressive waves. While it does not transfer net energy, it still represents a wave phenomenon with energy oscillation within its segments.
Assertion (A): In a harmonic wave of a given frequency all particles have the same amplitude but different phases at a given time.
Reason (R): In a stationary wave, all particles have the same phase at a given instant but have different amplitudes.
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
In a harmonic traveling wave, all particles oscillate with the same amplitude but their phases vary with position. So, (A) is true. In a stationary wave, particles between two successive nodes vibrate in phase, but particles on either side of a node are \(180^\circ\) out of phase. Their amplitudes also vary with position. So, (R) is false.
Assertion (A): An acoustic guitar depends for its sound on the acoustic resonance produced in the hollow body of the instrument by the oscillations of the strings.
Reason (R): Electric guitar is a solid instrument that based upon resonance. (In electric guitar the oscillations of the metal strings are sensed by electric “pickups” that send it to an amplifier).
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
An acoustic guitar uses the resonance of its hollow body to amplify and shape the sound produced by vibrating strings, so (A) is true. An electric guitar, being a solid-body instrument, generates sound via electromagnetic pickups sensing string vibrations, which are then amplified electronically. It does not rely on acoustic body resonance for sound production. Thus, Reason (R) is false.
Assertion (A): In a stationary-wave system, displacement nodes are pressure antinodes, and displacement antinodes are pressure nodes.
Reason (R): When a closed organ pipe vibrates, the pressure of the gas at the closed end remains constant.
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
In a stationary wave, displacement nodes correspond to points of maximum pressure variation (pressure antinodes) and displacement antinodes correspond to points of minimum pressure variation (pressure nodes). So, (A) is true.
At the closed end of an organ pipe, there must be a displacement node, which is a pressure antinode, meaning there is maximum pressure variation, not constant pressure. Thus, (R) is false.
Assertion (A): Both arms of a tuning fork vibrate with the same frequency.
Reason (R): The two arms of a tuning fork vibrate in phase.
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
Both arms of a tuning fork vibrate as a single system, thus at the same frequency. Assertion (A) is true.
For efficient sound production, the arms vibrate 180 degrees out of phase (in opposite directions), not in phase. Therefore, Reason (R) is false.
Assertion (A): The energy stored by a stationary wave is zero.
Reason (R): When two identical waves travelling in opposite directions superimpose, their whole energy is converted into heat.
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 false; a stationary wave stores energy, which oscillates between kinetic and potential forms.
Reason (R) is false; energy is not converted to heat but redistributed to form the stationary wave pattern.
Assertion (A): In \(n^{\text{th}}\) normal mode of a stretched string, there are \(n\) antinodes and \((n+1)\) nodes.
Reason (R): The ends of string are nodes, so the number of nodes is one more than the number of antinodes.
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. For a stretched string fixed at both ends, the \(n^{\text{th}}\) normal mode indeed has \(n\) antinodes and \(n+1\) nodes.
Reason (R) is true and correctly explains this: the fixed ends are always nodes, leading to one more node than antinode.