( This ( ( is ( ( the reason ) ( why ( ( a ( concave lens ) ) ( is ( called ( a ( diverging lens ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ is) (NP (NP (DT the) (NN reason)) (SBAR (WHADVP (WRB why)) (S (NP (DT a) (JJ concave) (NN lens)) (VP (VBZ is) (VP (VBN called) (NP (DT a) (VBG diverging) (NN lens)))))))) (. .)))
This is the reason why a concave lens is called a diverging lens.
(ROOT (S (NP (JJ Concave) (NNS lenses)) (VP (MD can) (VP (VB correct) (NP (NN myopia)))) (. .)))