Class 9 Practice Level 3 – Sound – Set 2 Leave a Comment / By Gulam Hamza / July 11, 2024 Class 9 Practice Level 3 - Sound - Set 2 Total questions: 15 1. The speed of sound in a medium is 400 m/s, and its wavelength is 2 meters. What is the frequency of the sound wave? 100 Hz 200 Hz 300 Hz 400 Hz None 2. A string fixed at both ends has a length of 1 meter and a speed of 340 m/s. What is the frequency of its first overtone? 170 Hz 340 Hz 510 Hz 680 Hz None 3. If the sound pressure level is 90 dB, what is the sound pressure (in Pascals) if the reference pressure is $ \displaystyle 2\times {{10}^{{-5}}}\text{ Pa}?$ 0.02 Pa 0.2 Pa 2 Pa 20 Pa None 4. If two sound waves with frequencies of 500 Hz and 510 Hz are played together, what is the beat frequency? 5 Hz 10 Hz 15 Hz 20 Hz None 5. A sound wave takes 3 seconds to travel from point A to point B and back to point A after reflection. If the speed of sound in the medium is 300 m/s, what is the distance between point A and point B? 225 meters 450 meters 675 meters 900 meters None 6. A sound wave has a frequency of 850 Hz and a wavelength of 0.4 meters. What is the speed of sound in the medium? 320 m/s 340 m/s 360 m/s 380 m/s None 7. A sound wave is reflected off a wall and returns to the source in 6 seconds. If the speed of sound is 340 m/s, how far is the wall from the source? 510 meters 1020 meters 1530 meters 2040 meters None 8. Two sound waves with frequencies of 530 Hz and 540 Hz are played together. What is the beat frequency? 5 Hz 10 Hz 15 Hz 20 Hz None 9. A string fixed at both ends has a length of 2 meters and a fundamental frequency of 85 Hz. What is the frequency of its third harmonic? 170 Hz 255 Hz 340 Hz 425 Hz None 10. A pipe open at both ends has a length of 1.5 meters. If the speed of sound is 340 m/s, what is the fundamental frequency of the pipe? 56.7 Hz 113.3 Hz 226.7 Hz 340 Hz None 11. An observer is moving away from a stationary sound source at a speed of 15 m/s. The source emits a frequency of 400 Hz. What is the observed frequency if the speed of sound is 340 m/s? 362 Hz 375 Hz 383 Hz 390 Hz None 12. The sound intensity at a distance of 1 meter from a source is 90 dB. What will be the intensity level at a distance of 3 meters from the source? 80 dB 82 dB 84 dB 86 dB None 13. A sound wave has an amplitude of 0.03 meters and a frequency of 250 Hz. What is the maximum speed of the particles of the medium through which the sound is traveling? (Assume the speed of sound in the medium is 340 m/s) 3 m/s 4.7 m/s 5 m/s 6 m/s None 14. A string fixed at both ends has a length of 1.2 meters and produces a second harmonic frequency of 200 Hz. What is the speed of the wave on the string? 240 m/s 300 m/s 400 m/s 480 m/s None 15. If the sound pressure level is 100 dB, what is the sound pressure (in Pascals) if the reference pressure is $ \displaystyle 2\times {{10}^{{-5}}}\text{Pascals}?$ 0.02 Pa 0.2 Pa 2 Pa 20 Pa None 1 out of 15 Time's up