http://www.elateafrica.org/elate/physics/waves/traqnsversewaves.jpg Note that : Leaf. A has attained maximum displacement and is about to start going down . Leaves B, C and D are still going up. Each of them will finally attain its maximum displacement and then move downwards to complete the cycle. Leaf E is at the lowest displacement and it is about to start going upwards. Leaves F, G, and H are still going downward and so on. I have a problem with point 2 and 4. How can leaves B,C and D go up when the crest is at point A? I thought that in a wave, there are only certain points in waves that are crests and troughs, and these are separated by some distance called wavelengths? If so, how could there be so many crests, at leaves B,C, and D, and so many troughs at F, G and H? Could someone point out my fault in my understanding?