Question

a sound wave has a frequency 2hz and length 40 cm .how long will it take to travel 1.6 km

Answer 1

We know that speed of a wave is its frequency times its wavelength . 
 The speed of the above mentioned sound is 2hz×0.4m
⇒0.8m/s. 1.6 km=1600 m.
Time taken=distance÷velocity 
⇒1600m÷0.8m/s 
⇒2000s