A bat can detect small objects such as an insect whose size is approximately equal to the wavelength of the sound the bat makes.
What is the smallest insect a bat can detect? Assume that bats emit a chirp at a frequency of 47.6 kHz, and that the speed of sound in air is 413 m/s. Answer in units of mm.
Machines makes work easier by increasing the amount of force that is applied, and changing the direction in which the force is applied !! Hope it helped (p.s. I had this same question)