# CBSE Important Questions(Long questions) for Our Environment

Assignments NCERT Solutions

Given below are the Class 9 Maths Long questions for Sound
1. A person hears an echo from the top of a tower, 2.2 sec after the sound is produced. How far away is the tower from the person? Speed of the sound in air is 332m/s?
2. How can multiple echoes of a single sound be produced? Explain?
3. Define echo. Give its two application?
4. When a sound is reflected from a distant object, an echo is produced and heard on a winter night. Will you hear the echo of the same sound on a summer day if the distance between reflecting surface and the source of sound remains the same? Justify your answer?
5. Why are the walls and roof of an auditorium covered with sound absorbent materials?
6. Define reverberation. What arrangements should be made in an auditorium to control excessive reverberation?
7. Determine the minimum distance between the listener and reflector for an echo to be heard dintinctively of a sound propagating with a speed v m/s?
8. Name the sound of the following frequencies:
a) 5Hz
b) 50Hz
c) 50000Hz
d) 50kHz
9. Write full form of acronym SONAR. How the method of echo-ranging is used to detetmine the depth of the sea?
10. Explain, how defects in a metal block can be detected using ultrasound?
11. How bats can detect their prey?
12. What is the frequency of a wave whose time period is 0.05s?
13. A ship is stationary is at a distance of 2800m from the sea-bed. The ship sends an ultrasound signal to the sea-bed and its echo is heard after 4s. Find the speed of sound in water?
14. A body is vibrating 6000times in one minute. If the velocity of sound in air is 360m/s, Find:
a) Frequency of the vibration in Hz
b) Wavelength of sound produced
15. Explain with the help of a diagram the working of SONAR?
16. A hospital uses an ultrasonic scanner to locate tumors in a tissue. What is the wavelength of ultrasound in a tissue in which the speed of ultrasound is 1.5km/sec2 ? The operating frequency of the scanner is 4.0 MHz?
17. State any two characteristics of a wave motion?
18. A ship sends out ultrasound that returns from the sea-bed and is detected after 3.22sec. If the speed of ultrasound in sea water is 1530m/s, calculate the distance of the sea-bed from the ship?
19. How do the frequency and amplitudes affect musical sound?
20. Explain how the human ear works?