( ( ( The image ) ( in ( a ( plane mirror ) ) ) ) ( ( ( is ( ( the ( same distance ) ) ( behind ( the mirror ) ) ) ) ( as ( ( the object ) ( is ( in ( front ( of ( the mirror ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN image)) (PP (IN in) (NP (DT a) (NN plane) (NN mirror)))) (VP (VBZ is) (NP (NP (DT the) (JJ same) (NN distance)) (PP (IN behind) (NP (DT the) (NN mirror)))) (SBAR (IN as) (S (NP (DT the) (NN object)) (VP (VBZ is) (PP (IN in) (NP (NP (NN front)) (PP (IN of) (NP (DT the) (NN mirror))))))))) (. .)))
The image in a plane mirror is the same distance behind the mirror as the object is in front of the mirror.
(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)))))))) (. .)))