Question 2.14* from 'OPTICS' 4th edition by Eugene Hecht.
See attached file for full problem description.
(a) wavelength = distance between nearest repetitions of the same = 30 cm
(c) frequency = speed / wavelength = 100 cm/s / 30 cm = 3.3333 Hz
(b) period = 1/frequency = 0.3 sec: wave.jpg file with the plot is attached
There is missing ...