(a) The sound of which of the following frequencies are audible' to human ears : 2 Hz, 5 Hz, 20 Hz, 200 Hz, 2000 Hz. (b) How moths of certain families are able to escape capture?


#1

(a) 20 Hz, 200 Hz and 2000 Hz.

(b) They do not reflect the ultrasounds sent towards them by bats.