( Eventually ( , ( ( ( the ( two parts ) ) ( of ( the wave ) ) ) ( ( are ( made ( to ( recombine ( on ( a surface ) ) ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB Eventually)) (, ,) (NP (NP (DT the) (CD two) (NNS parts)) (PP (IN of) (NP (DT the) (NN wave)))) (VP (VBP are) (VP (VBN made) (S (VP (TO to) (VP (VB recombine) (PP (IN on) (NP (DT a) (NN surface)))))))) (. .)))
Eventually, the two parts of the wave are made to recombine on a surface.
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD two) (NNS types)) (PP (IN of) (NP (NN surface) (NNS waves))))) (. .)))