( ( For ( visible light ) ) ( , ( ( a quantum ) ( ( is ( called ( a photon ) ) ) . ) ) ) )
(ROOT (S (PP (IN For) (NP (JJ visible) (NN light))) (, ,) (NP (DT a) (NN quantum)) (VP (VBZ is) (VP (VBN called) (NP (DT a) (NN photon)))) (. .)))
For visible light, a quantum is called a photon.
(ROOT (S (NP (PRP We)) (VP (VBP call) (NP (DT the) (JJ only) (NN light)) (SBAR (IN that) (S (NP (NNS people)) (VP (MD can) (VP (VB see) (NP (JJ visible) (NN light))))))) (. .)))