Question

48. Ultrasonic waves have frequencies
a. Below 20 Hz
b. Between 20 Hz and 20,000 Hz
c. Above 20,000 Hz
d. No lower or upper limit of frequency​

Answer 1

Ultrasonic waves have frequencies above 20,000 Hz

Answer 2

Answer:

D. Above 20000 Hz

Explanation:

Below 20hz is called infra sonic

And

Bet. 20hz and 20000 hz is normal as humans can hear only between this range.