( ( ( Two sources ) ( of disturbance ) ) ( ( create ( ( ( two sets ) ( of ( concentric waves ) ) ) ( that ( ( ( form ( an ( interference pattern ) ) ) ( at points ) ) ( where ( ( the waves ) overlap ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (CD Two) (NNS sources)) (PP (IN of) (NP (NN disturbance)))) (VP (VBP create) (NP (NP (CD two) (NNS sets)) (PP (IN of) (NP (JJ concentric) (NNS waves))) (SBAR (WHNP (WDT that)) (S (VP (VBP form) (NP (DT an) (NN interference) (NN pattern)) (PP (IN at) (NP (NNS points))) (SBAR (WHADVP (WRB where)) (S (NP (DT the) (NNS waves)) (VP (VBP overlap))))))))) (. .)))
Two sources of disturbance create two sets of concentric waves that form an interference pattern at points where the waves overlap.
(ROOT (S (NP (JJ Constructive) (NN interference)) (VP (VBZ is) (SBAR (WHADVP (WRB when)) (S (NP (CD two) (NNS waves)) (VP (VBP combine) (S (VP (TO to) (VP (VB create) (NP (DT a) (JJR larger) (NN wave))))))))) (. .)))