( ( In ( ( the case ) ( of ( plane mirrors ) ) ) ) ( , ( ( the image ) ( ( is ( said ( to ( be ( a ( virtual image ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (NP (DT the) (NN case)) (PP (IN of) (NP (NN plane) (NNS mirrors))))) (, ,) (NP (DT the) (NN image)) (VP (VBZ is) (VP (VBN said) (S (VP (TO to) (VP (VB be) (NP (DT a) (JJ virtual) (NN image))))))) (. .)))
In the case of plane mirrors, the image is said to be a virtual image .
(ROOT (S (NP (DT A) (NN plane) (NN mirror)) (VP (VP (VBZ has) (NP (DT a) (ADJP (JJ flat) (JJ reflective)) (NN surface))) (CC and) (VP (VBZ forms) (NP (RB only) (JJ virtual) (NNS images)))) (. .)))