On a slinky,we can produce:

Mention one practical use of echoes.

$(a)$ What is the audible range of the average human ear?
$(b)$ Explain how ultrasound is used to clean spiral tubes and electronic components?

Given that sound travels in air at $340 \, m s^{-1}$,find the wavelength of the waves in air produced by a $20 \, Hz$ sound source. If the same source is put in a water tank,what would be the wavelength of the sound waves in water? (Given,speed of the sound in water $= 1480 \, m s^{-1}$)

Define frequency,amplitude,and speed of a sound wave.

State whether the following statement is true or false:
Light waves require no medium for their propagation.