Find the wavelength of sound for frequencies up to 120 kHz at which a bat can hear it. Take the speed of sound in air as 344 m

Frequency = v / $\lambda $

Velocity of sound in air , v = 344m/s

Frequency = 120kHz = 120000Hz

$\lambda $ = 344/120000

$\lambda $ = 0.00286666

$\lambda $ = 2.8 x ${{10}^{-3}}$