The phrases "the nanometers of a straight line between two crests" and "the distance in nanometers of the length of the wave between two crests" have slightly different meanings when describing the measurement between two crests in a wave.
"The nanometers of a straight line between two crests": This phrase suggests that we are referring to the measurement of the distance between two crests by considering a straight line connecting them. It implies a direct, linear measurement along a straight path between the two points. This measurement represents the spatial separation between the two crests and is typically associated with the physical distance between them.
"The distance in nanometers of the length of the wave between two crests": This phrase emphasizes the "length of the wave" and indicates that we are referring to the wavelength between two crests. It implies measuring the entire length of one complete wave cycle, which includes a crest, a trough, and the distance between them. It is a measure of the spatial extent of one full oscillation of the wave. The wavelength is typically represented by the Greek letter lambda (λ) and is commonly used to describe the size or scale of a wave.
In summary, while both phrases involve measuring the distance between two crests in a wave, the first phrase focuses on the straight-line distance between the crests, while the second phrase emphasizes the measurement of the wavelength, encompassing one complete cycle of the wave.