An increase in amplitude makes a sound wave _______.

Sounds that are pleasant to hear are called ultrasounds.

Ultrasounds are high frequency sounds.

Communication in the submarines is using infra waves.

The device that transmits ultrasounds in SONAR is called _______.

• A receiver receives the sound reflected from the depths of the sea and perceives it. 

Sound cannot travel through _________.

Echo is _________ of the sound.

• Refraction is the bending of sound waves when they enter from one medium to another medium.

The reflection of sound in a closed surface is called _______.

• Amplification refers to the increase of the amplitude or loudness of sound.
• The repetition of a sound that is caused by the reflection of sound wave in large spaces is called an echo.

Which of the below is used to amplify sound?

Units to measure sound:

• The unit of power is watt.
• The unit of force is newton.
• The unit of work is Joule.

SONAR is used in _______

A sonar can detect the enemy ship using
_________ .

Distance can be measured in___________.

• The SI unit of time is Second.
• The SI unit of pressure is Pascal.
• The SI unit of force is Newton.

Music is heard from a vehicle's horn.

The SI unit of measurement of velocity is kg/s.

A guitar can produce __________.

Sound from a speaker undergoes an echo to reach the source back from a mountain located at a distance of 340 m from the source. The total time taken by the sound to cover this distance is 2 s. The speed of sound is ___ m/s.

After echo, the total distance travelled = 2d