( ( An ( ( extremely fast ) spherical ) ) ( ( ( ( mirror ( gathers light ) ) and ) ( ( focuses ( the image ) ) ( on ( the ( film plane ) ) ) ) ) . ) )
(ROOT (S (NP (DT An) (ADJP (RB extremely) (JJ fast)) (NN spherical)) (VP (VP (VBP mirror) (S (NP (NNS gathers)) (ADJP (JJ light)))) (CC and) (VP (VBZ focuses) (NP (DT the) (NN image)) (PP (IN on) (NP (DT the) (NN film) (NN plane))))) (. .)))
An extremely fast spherical mirror gathers light and focuses the image on the film plane.
(ROOT (S (NP (NNP Plane) (NNS mirrors)) (VP (VBP work) (SBAR (IN because) (S (NP (DT the) (JJ light) (NNS rays)) (VP (VBP create) (NP (NP (DT a) (JJ virtual) (NN image)) (PP (IN behind) (NP (DT the) (NN mirror)))))))) (. .)))