A certain type of laser emits light that has a frequency of 5.2 1014 Hz. The

Question:

A certain type of laser emits light that has a frequency of 5.2 × 1014 Hz. The light, however, occurs as a series of short pulses, each lasting for a time of 2.7 × 10-11 s.
(a) How many wavelengths are there in one pulse?
(b) The light enters a pool of water. The frequency of the light remains the same, but the speed of the light slows down to 2.3 × 108 m/s. How many wavelengths are there now in one pulse?