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Imagine and create your own visuals in mind, believe me that it'll help you relate and remember the concepts much well.
For example, I understood the concept of Crests and troughs by observing the movement of sand particles on the floor of a moving bus.
For your better understanding, let's know that, Waves have moving crests (or peaks) and troughs. A crest is the highest point the medium rises to and a trough is the lowest point the medium sinks to.
So, when I saw the sand particles accumulating on a particular point and they were following a special pattern. I saw a pattern !!
Yes ! That was a wave !
Places where sand particles were accumulating was troughs and the mid-distance between 2 troughs was crests !
