A bat emits ultrasonic sound of frequency 1000 kHz in air. If the sound meets a water surface, what is the wavelength of (a) the reflected sound, (b) the transmitted sound? Speed of sound in air is 340 m s^–1 and in water 1486 m s^–1.

(a) Frequency of the ultrasonic sound, ν = 1000 kHz = 10⁶ Hz 
Speed of sound in air, v_a = 340 m/s 
The wavelength (λ_r) of the reflected sound is given by the relation, 
λ_r = v/v 

    = 340/10⁶ 
    = 3.4 × 10^-4 m.
(b) Frequency of the ultrasonic sound, ν = 1000 kHz
                                                             = 10⁶ Hz 
Speed of sound in water, v_w = 1486 m/s 
The wavelength of the transmitted sound is given as, 
λ_r = 1486 × 10⁶
    = 1.49 × 10^-3 m.