Humpback whales are known to produce a collection of elaborate and repeating sounds with frequencies starting at 20 Hz. The sound waves travel through water at speeds of approximately 1400 m/s. Determine the wavelengths of the waves at the for this starting frequency.

Amichelson interferometer operating at a 600 nm wavelength has a 3.02-cm-long glass cell in one arm. to begin, the air is pumped out of the cell and mirror m2 is adjusted to produce a bright spot at the center of the interference pattern. then a valve is opened and air is slowly admitted into the cell. the index of refraction of air at 1.00 atm pressure is 1.00028.how many bright-dark-bright fringe shifts are observed as the cell fills with air?