( ( ( The ( light beam ) ) ( ( ( ( passing ( from ( a medium ) ) ) ( where ( it ( ( goes ( at ( ( one speed ) ( , ( ( c 1 ) , ) ) ) ) ) ( into ( ( a ( second medium ) ) ( where ( it ( goes ( at ( a ( different speed ) ) ) ) ) ) ) ) ) ) ) ) , ) ( c 2 ) ) ) ( , ( ( ( will always ) ( take ( ( the path ) ( of ( least time ) ) ) ) ) . ) ) )
(ROOT (S (NP (NP (DT The) (JJ light) (NN beam)) (VP (VBG passing) (PP (IN from) (NP (DT a) (NN medium))) (SBAR (WHADVP (WRB where)) (S (NP (PRP it)) (VP (VBZ goes) (PP (IN at) (NP (NP (CD one) (NN speed)) (PRN (, ,) (FRAG (X (SYM c)) (NP (CD 1))) (, ,)))) (PP (IN into) (NP (NP (DT a) (JJ second) (NN medium)) (SBAR (WHADVP (WRB where)) (S (NP (PRP it)) (VP (VBZ goes) (PP (IN at) (NP (DT a) (JJ different) (NN speed))))))))))) (, ,) (FRAG (X (SYM c)) (NP (CD 2))))) (, ,) (VP (MD will) (ADVP (RB always)) (VP (VB take) (NP (NP (DT the) (NN path)) (PP (IN of) (NP (JJS least) (NN time)))))) (. .)))
The light beam passing from a medium where it goes at one speed, c 1 , into a second medium where it goes at a different speed, c 2 , will always take the path of least time.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NN light)) (VP (VBZ passes) (PP (IN from) (NP (CD one) (NN medium))) (PP (TO to) (NP (DT another)))))) (, ,) (NP (PRP it)) (VP (VBZ changes) (NP (NN speed))) (. .)))