Give two practical applications of reflection of sound waves.
Solution and Explanation
(i) SONAR, which stands for Sound Navigation and Ranging, utilizes the reflection of sound to measure the speed and distance of underwater objects.
(ii) The functioning of a stethoscope involves multiple reflections of sound, allowing the sound of a patient's heartbeat to reach the doctor's ear.
Top CBSE Class IX Questions
- The following table gives the lifetimes of 400 neon lamps:
Length (in hours)
Number of lamps
300 − 400
14
400 − 500
56
500 − 600
60
600 − 700
86
700 − 800
74
800 − 900
62
900 − 1000
48
(i) Represent the given information with the help of a histogram.
(ii) How many lamps have a lifetime of more than 700 hours? - Give an example to show that even as a young girl Santosh was not ready to accept anything unreasonable.
- Where was Abdul Kalam’s house?
- What do you think Dinamani is the name of? Give a reason for your answer.
Why was Santosh sent to the local school?
Concepts Used:
Sound
Sound is a vibration that propagates the mechanical wave of displacement and pressure, through a medium can be of any matter. In other words, the sound is the thin line between Music sound and Noise.
Types of Sounds:
Sound can be divided into two types depending on its frequency. The following are:-
Infrasonic Waves:
- Infrasonic waves have a frequency lower than 20 Hz. Since it is below the human hearing range, it is inaudible to humans.
- However, several other living organisms use these waves to communicate, whales, sharks, elephants, hippopotamus, etc. these waves are also used in the scientific field, it is used to study upcoming earthquakes, volcanic eruptions, human heart rates, rock formation stages, etc.
Ultrasonic waves:
- Ultrasonic waves have a frequency higher than 20 kHz. Since it is above the human hearing range, it is inaudible to humans.
- These waves are used in the scientific field, it is used to study human heart rates, to take sonograms, navigation of directions, imaging things, uniform sample mixing, communication, testing of samples, etc.