Question

Which of the following correctly represents the increasing order of frequency for infrasound, ultrasound, and audible range?

Answer 1

1. Infrasound frequency is less than $20Hz$
2. Audible range frequency lies between(and including) $20Hz$ and $20kHz$.
3. Ultrasound frequency is greater than $20kHz$:

Hence, the order of increasing frequency is infrasound<audible range<ultrasound.