In which medium does sound travel the fastest? a. salt water b. fresh water c. air *** d. cast iron a wave has a wavelength of 10 mm and a frequency of 5 hertz. what is its speed? a. 50 mm/s b. 50 hertz/s c. 2 mm/s 0.50 mm/s how does reflection differ from refraction and diffraction? a. reflection is the only process in which the wave does not continue moving forward. b. reflection is the only process that involves a change in the wave. c. reflection affects all types of mechanical waves, but refraction and diffraction do not. d. reflection is the only process that changes the direction.