One face of a rectangular glass plate 6 cm thick is silvered. An object held 8 cm in front of the first face, forms an image 12 cm behind the silvered face. The refractive index of the glass is
(a) 0.4 (b) 0.8
(c) 1.2 (d) 1.6
(c) Let x be the apparent position of the silvered surface.
According to property of plane mirror