Question

List two applications of reflection of sound.

Answer 1

Sound

1. When a body undergoes vibration, it transfers this vibration energy to the air particles around it.
2. These air particles suffer compression and rarefaction.
3. By repeated compression and rarefaction they transfer their energy into the neighbouring particles.
4. In this way, the sound energy travels a distance through the medium and sound can be heard.
5. The speed of sound in air is $340m/s$, their speed in water is $1480m/s$ and in solid is around $6000m/s$.

Applications of Reflection of Sound

• SONAR

1. The term SONAR is an acronym for Sound Navigation and Ranging and is employed for underwater detection, ranging, and depth measurement.
2. Due to the high attenuation of electromagnetic waves in seawater, radio communication between submerged submarines in a sea is not possible.
3. Since the attenuation of sound waves in water is low, ultrasonic waves are used for underwater communication.
4. SONAR which is used for the detection of submarines, icebergs, and other underwater objects in the ocean, finding the depth of the sea, direction signaling, etc. utilizes ultrasonics for the purpose.
5. A sharp ultrasonic beam is directed in various directions into the sea and is picked up on return after reflection.
6. The time interval between the transmission of ultrasonic waves and the reception of reflected ultrasonic waves gives the distance it and the change in frequency of the echo signal due to the Doppler effect can give the velocity of the body and its direction.

• Medical Applications

1. In the medical field as well, ultrasonics are finding ever-increasing applications.
2. The body parts affected by neuralgic or rheumatic pains on being exposed to ultrasonics get sufficient relief from pains.
3. Ultrasonic waves are passed into the body and their echoes, as they are reflected back from surfaces between organs and structures in the body, are recorded.
4. The beam moves like a cone from the source and as it strikes a structure normally, it gets reflected back directly to its source.
5. An example of this is ultrasonography for medical diagnosis, e.g., retinal detachment, lens dislocation, intraocular tumors, fetus in a womb, etc.