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Q. No.A wave pulse travels along a taut string towards a fixed end as shown in the adjacent figures:
The reflected pulse is correctly shown by:
The reflected pulse is correctly shown by:
| 1. |  |
2. |  |
| 3. |  |
4. |  |
Subtopic: Wave Motion |
Level 4: Below 35%
Hints
The equation of vibration of a taut string, fixed at both ends, is given by; \(y=(3~\text{mm})~\text{cos}\left(\dfrac{\pi x}{10~\text{cm}}\right)~\text{sin}(800\pi~\text{s}^{-1}{t}).\) The positions of the nodes are:
| 1. | \(x= 0~\text{cm}, 10~\text{cm}, 20~\text{cm},....\) |
| 2. | \(x= 0~\text{cm}, 20~\text{cm}, 40~\text{cm},....\) |
| 3. | \(x= 5~\text{cm}, 10~\text{cm}, 15~\text{cm},....\) |
| 4. | \(x= 5~\text{cm}, 15~\text{cm}, 25~\text{cm},....\) |
Subtopic: Beats |
Level 4: Below 35%
Hints
Sinusoidal sound waves of the same frequency travelling in air along the \(x\)-axis and the \(y\)-axis arrive in phase with each other at the origin. Their amplitudes are equal to \(A\) (each). The amplitude of the vibration at the origin is:
| 1. | \(A\) | 2. | \(\sqrt 2A\) |
| 3. | \(2A\) | 4. | \((2+\sqrt2)A\) |
Subtopic: Wave Motion |
Level 4: Below 35%
Hints
When two identical loudspeakers playing the same frequency are placed equidistant from an observer, a sound of \(60\) dB is heard if the sources are in phase with each other. However, if the two speakers are out of phase, no sound is heard. If the speakers are played with a phase difference of \(90^\circ,\) the sound heard will be:
1. \(30\sqrt2\) dB
2. \((60+\sqrt2)\) dB
3. \(57\) dB
4. \(60\sqrt2\) dB
1. \(30\sqrt2\) dB
2. \((60+\sqrt2)\) dB
3. \(57\) dB
4. \(60\sqrt2\) dB
Subtopic: Pressure Wave in Sound |
Level 4: Below 35%
Hints
The equation of vibration of a taut string, fixed at both ends, is given by: \(y=(4~\text{mm})~\cos\left(\dfrac{\pi x}{30~\text{cm}}\right)~\sin\Big(400\pi s^{-1}t\Big) \)
At which points is the amplitude equal to \(2\) mm?
At which points is the amplitude equal to \(2\) mm?
| 1. | \(x = \) \(10\) cm, \(20\) cm, \(30\) cm, \(40\) cm |
| 2. | \(x=\) \(10\) cm, \(15\) cm, \(30\) cm, \(45\) cm |
| 3. | \(x =\) \(10\) cm, \(20\) cm, \(40\) cm, \(80\) cm |
| 4. | \(x = \) \(10\) cm, \(20\) cm, \(40\) cm, \(50\) cm |
Subtopic: Standing Waves |
Level 3: 35%-60%
Hints
A string \((AB)\) under tension has a fundamental frequency of \(120~\text{Hz}.\) The string is set into vibration and a point \(P\) is held down by a finger so that it becomes a node (i.e., \(P\) does not vibrate):\(\Large\frac{AP}{PB}=\frac12.\) The lowest frequency for which this happens is:
1. \(120~\text{Hz}\)
2. \(240~\text{Hz}\)
3. \(360~\text{Hz}\)
4. \(180~\text{Hz}\)
1. \(120~\text{Hz}\)
2. \(240~\text{Hz}\)
3. \(360~\text{Hz}\)
4. \(180~\text{Hz}\)
Subtopic: Travelling Wave on String |
Level 3: 35%-60%
Hints
Given below are two statements:
| Statement I: | Sound waves travelling from air into water, incident obliquely, bend towards the normal. |
| Statement II: | Sound waves travel more slowly in water than in air. |
| 1. | Statement I is incorrect and Statement II is correct. |
| 2. | Both Statement I and Statement II are correct. |
| 3. | Both Statement I and Statement II are incorrect. |
| 4. | Statement I is correct and Statement II is incorrect. |
Subtopic: Speed of Sound |
Level 3: 35%-60%
Hints
When sound waves produced under water emerge into the air, then:
| 1. | the frequency increases, and wavelength decreases. |
| 2. | the frequency remains constant, but the wavelength decreases. |
| 3. | the frequency decreases, wavelength remains constant. |
| 4. | the frequency remains constant but the wavelength increases. |
Subtopic: Speed of Sound |
Level 3: 35%-60%
Hints
A gas is taken in a closed transparent tube, some lycopodium powder is spread within the tube, and the tube is placed horizontally. When the mouth of the tube is vibrated with a tuning fork of frequency \(1~\text{kHz,}\) and the length of the tube is adjusted: the powder is observed to collect in a wave-like pattern with adjacent 'maxima' separated by \(20~\text{cm}.\) The speed of sound in the gas is:
| 1. | \(100~\text{m/s}\) | 2. | \(200~\text{m/s}\) |
| 3. | \(400~\text{m/s}\) | 4. | \(800~\text{m/s}\) |
Subtopic: Speed of Sound |
Level 3: 35%-60%
Please attempt this question first.
Hints
Please attempt this question first.
Two different sources of sound having slightly different periods of vibration: \(1~\text{ms}\) and \(1.01~\text{ms},\) are sounded together. The resulting beat frequency is nearly:
1. \(100~\text{Hz}\)
2. \(50~\text{Hz}\)
3. \(10~\text{Hz}\)
4. \(0.01~\text{Hz}\)
1. \(100~\text{Hz}\)
2. \(50~\text{Hz}\)
3. \(10~\text{Hz}\)
4. \(0.01~\text{Hz}\)
Subtopic: Beats |
Level 3: 35%-60%
Hints
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