( ( The lens ) ( ( focuses ( light rays ) ) . ) )
(ROOT (S (NP (DT The) (NN lens)) (VP (VBZ focuses) (NP (JJ light) (NNS rays))) (. .)))
The lens focuses light rays.
(ROOT (S (NP (NNP Convex) (NNS lenses)) (VP (VBP are) (NP (NP (JJR thicker)) (PP (IN in) (NP (DT the) (NN middle)))) (PP (IN than) (PP (IN at) (NP (DT the) (NNS edges)))) (SBAR (IN so) (S (NP (PRP they)) (VP (VBP cause) (S (NP (NP (NNS rays)) (PP (IN of) (NP (NN light)))) (VP (TO to) (VP (VB converge) (, ,) (CC or) (VB meet) (, ,) (PP (IN at) (NP (NP (DT a) (NN point)) (VP (VBN called) (NP (NN focus)))))))))))) (. .)))