Question

Ans:
d) State whether the following statements are true or false :
i) Infrasound has frequency greater than 20000 Hz.
2)Ultrasonic waves are used to kill bacteria in liquids like milk.
3) the speed of sound in a soild is greater than that in a liquid.
4) a hard and surface is a good reflector of the sound .​

Answer 1

Answer:

i ) false

2) false

3) false

4 ) true

Answer 2

Answer:

1) Infrasound has frequency greater than 20000 Hz : FALSE

REASON : The sound waves of frequency greater than 20000 Hz are called ultrasonic waves.  

2)Ultrasonic waves are used to kill bacteria in liquids like milk : TRUE

REASON : Ultrasonic vibration also can be used to kill bacteria in milk and other liquids.

3) The speed of sound in a solid is greater than that in a liquid : TRUE

REASON : Speed of sound is greater in solids than in liquids because. Speed of sound depends upon the elasticity which is higher in case of solid then liquid.

4) A hard and surface is a good reflector of the sound : TRUE

REASON : Hard surfaces, such as ceramic tile, gypsum board, or wood, tend to reflect sound waves, causing ‘echo’. Reverberation is the term used to describe sound waves that are reflected off of surfaces.