( ( ( ( ( This ( is ( because ( optics ( deals ( with ( ( the behavior ) ( of light ) ) ) ) ) ) ) ) , ) and ) ( light ( is ( ( one example ) ( of ( an ( electromagnetic wave ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (DT This)) (VP (VBZ is) (SBAR (IN because) (S (NP (NNS optics)) (VP (VBZ deals) (PP (IN with) (NP (NP (DT the) (NN behavior)) (PP (IN of) (NP (NN light)))))))))) (, ,) (CC and) (S (NP (NN light)) (VP (VBZ is) (NP (NP (CD one) (NN example)) (PP (IN of) (NP (DT an) (JJ electromagnetic) (NN wave)))))) (. .)))
This is because optics deals with the behavior of light, and light is one example of an electromagnetic wave.
(ROOT (S (NP (NNS Optics)) (VP (VBZ explains) (NP (NP (DT the) (NN behavior)) (PP (IN of) (NP (JJ visible) (ADJP (JJ light) (CC and) (JJ electromagnetic)) (NNS waves))))) (. .)))