( ( When ( light ( strikes ( a surface ) ) ) ) ( , ( it ( ( is ( either ( ( ( ( absorbed , ) reflected ) or ) transmitted ) ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NN light)) (VP (VBZ strikes) (NP (DT a) (NN surface))))) (, ,) (NP (PRP it)) (VP (VBZ is) (VP (RB either) (VBN absorbed) (, ,) (VBN reflected) (CC or) (VBN transmitted))) (. .)))
When light strikes a surface, it is either absorbed, reflected or transmitted.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NN light)) (VP (VBZ meets) (NP (NN matter))))) (, ,) (NP (PRP it)) (VP (MD may) (VP (VB be) (VP (VP (VBN reflected)) (, ,) (VP (VBN transmitted)) (, ,) (CC or) (VP (VBN absorbed))))) (. .)))