( ( ( The lens ) ( in ( our eyes ) ) ) ( ( is ( ( ( an example ) ( of ( a ( convex lens ) ) ) ) ( which ( ( ( projects ( a ( real image ) ) ) ( on ( to ( ( the retina ) ( of ( the eye ) ) ) ) ) ) ( upside down ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN lens)) (PP (IN in) (NP (PRP$ our) (NNS eyes)))) (VP (VBZ is) (NP (NP (DT an) (NN example)) (PP (IN of) (NP (DT a) (NN convex) (NN lens))) (SBAR (WHNP (WDT which)) (S (VP (VBZ projects) (NP (DT a) (JJ real) (NN image)) (PP (IN on) (PP (TO to) (NP (NP (DT the) (NN retina)) (PP (IN of) (NP (DT the) (NN eye)))))) (ADVP (RB upside) (RB down))))))) (. .)))
The lens in our eyes is an example of a convex lens which projects a real image on to the retina of the eye upside down.
(ROOT (S (NP (NP (DT The) (NN lens)) (PP (IN of) (NP (DT the) (NN eye)))) (VP (VBZ is) (S (NP (DT a) (-LRB- -LRB-) (NN n) (-RRB- -RRB-) (NN convex)) (VP (VB shape)))) (. .)))