Howdy! can be replied to with just a nod and a smile. It simply means Hi! in Texan - not How are you doing?. Or you might reply, Hey Y'all Doon? if you want to engage in proper Texan interactions. Replying in proper English, well pronounced, with each syllable clearly spoken, is HIGHLY discouraged.
The crest of a wave is the point of maximum positive displacement, or upward movement, away from equilibrium, or an undisturbed state. The opposite of crest is trough, which is the point of the greatest negative, downward displacement.
A wavelength is how far apart a crest or trough is from another crest or trough. In a wave, there are many different characteristics, which include its amplitude and frequency. the amplitude is the distance between a wave's mid-point and it's crest or trough. Mathematically :   wavelength of sound wave = speed of the wave / frequency   where   wavelength is measured in meters   speed is measured meters/second   frequency is measured is Hz or second-1. 4 people found this useful.