SATHEE: Wave Motion 4 Question 7

Wave Motion 4 Question 7

7. A musician produce the sound of second harmonics from open end flute of $50 c m$ . The other person moves toward the musician with speed $10 k m / h$ from the second end of room. If the speed of sound $330 m / s$ , the frequency heard by running person will be

(2019 Main, 9 Jan II)

(a) $666 H z$

(b) $500 H z$

(d) $333 H z$

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Solution:

According to the question, the musician uses a open flute of length $50 c m$ and produce second harmonic sound waves

When the flute is open from both ends and produce second harmonic, then

$\begin{aligned} L & = λ_{2} \\ \Rightarrow f_{2} & = \frac{v}{L} \end{aligned}$

where, $λ_{2} =$ wavelength for second harmonic,

$f_{2} = frequency for second harmonic$

and $v =$ speed of wave.

For given question $\Rightarrow f_{2} = \frac{v}{L} = \frac{330}{50 \times 10^{- 2}}$

$f_{2} = 660 H z$ (frequency produce by source)

Now, a person runs towards the musician from another end of a hall

$v_{observer} = 10 k m / h (towards source)$

There is apparant change in frequency, which heard by person and given by Doppler’s effect formula

$\begin{aligned} \Rightarrow v^{'} & = f^{'} = v [\frac{v_{sound} + v_{observer}}{v_{sound}}] \\ f^{'} & = f_{2} [\frac{v_{s} + v_{o}}{v_{sound}}] \\ f^{'} & = 660 [\frac{330 + \frac{50}{18}}{330}] \\ f^{'} & = 666 H z \end{aligned}$

Hence, option (a) is correct.

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Wave Motion 4 Question 7

7. A musician produce the sound of second harmonics from open end flute of $50 c m$ . The other person moves toward the musician with speed $10 k m / h$ from the second end of room. If the speed of sound $330 m / s$ , the frequency heard by running person will be

Solution:

इंजीनियरिंग की तैयारी

चिकित्सा तैयारी

एनसीईआरटी पुस्तकें और समाधान

महत्वपूर्ण संसाधन

अन्य संसाधन

पाठ्यक्रम

परीक्षा मंच

नमूना मॉक टेस्ट

सदस्यता

एनसीईआरटी व्यायाम वीडियो समाधान

Wave Motion 4 Question 7

7. A musician produce the sound of second harmonics from open end flute of 50cm. The other person moves toward the musician with speed 10km/h from the second end of room. If the speed of sound 330m/s, the frequency heard by running person will be

Solution:

इंजीनियरिंग की तैयारी

चिकित्सा तैयारी

एनसीईआरटी पुस्तकें और समाधान

महत्वपूर्ण संसाधन

अन्य संसाधन

पाठ्यक्रम

परीक्षा मंच

नमूना मॉक टेस्ट

सदस्यता

एनसीईआरटी व्यायाम वीडियो समाधान

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7. A musician produce the sound of second harmonics from open end flute of $50 c m$ . The other person moves toward the musician with speed $10 k m / h$ from the second end of room. If the speed of sound $330 m / s$ , the frequency heard by running person will be