Question

Bats emit ultrasonic signals to navigate and hunt

They can catch insects as small in size as 1 wavelength

so, what insect is the smallest potential meal for a bat whose sonar (sound) frequency is 85,000 Hz?

Hint: sound velocity - 340m/sec

Possible answers :

150mm

3mm

20mm

4mm

2mm

Answer 1

as size is approximately equal to one wavelength of thesound

      the wave length will be thesize

    we have λ = v/n

where

   n is the frequency of the sound = 85000Hz

   v is the velocity of the sound = 340 m/s

             λ = 340 m/s /85000 Hz

                =4 *10^-3 m = 4 mm