Waves - NEET Physics Questions
Question 11: moderate

In the given progressive wave equation y = 0.5 sin (10πt – 5x); where x, y in cm and t in second. The maximum velocity of the particle is

1. 5 cm /sec
2. 5π cm /sec
3. 10 cm /sec
4. 10.5 cm /sec
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Question 12: moderate

The path difference between the two waves

\[ y_{1}= a_{1} sin \left( \omega t -\frac{2\Pi x}{\lambda} \right) \]

and

\[ y_{2}= a_{2} cos \left( \omega t -\frac{2\Pi x}{\lambda} + \varphi \right) \]

is

1. \[ \frac{\lambda}{2\Pi}\phi \]
2. \[ \frac{\lambda}{2\Pi}(\phi +\frac{\Pi}{2}) \]
3. \[ \frac{\lambda}{2\Pi}(\phi - \frac{\Pi}{2}) \]
4. \[ \frac{2\Pi}{\lambda}\phi  \]
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Question 13: moderate

The \(4^{\text{th}}\) overtone of a closed organ pipe is same as that of \(3^{\text{th}}\) overtone of an open pipe. The ratio of the length of the closed pipe to the length of the open pipe is:

1. 9 : 8
2. 7 : 9
3. 8 : 9
4. 9 : 7
View Answer

The frequency of the \(4^{\text{th}}\) overtone (9th harmonic) of a closed pipe is \(f_c = \frac{9v}{4L_c}\). The frequency of the \(3^{\text{rd}}\) overtone (4th harmonic) of an open pipe is \(f_o = \frac{4v}{2L_o} = \frac{2v}{L_o}\). Equating the two, \(\frac{9v}{4L_c} = \frac{2v}{L_o} ⇒ \frac{L_c}{L_o} = \frac{9}{8}\).