An object 2.4 m in front of a lens forms a sharp image on a film 12 cm behind lens . a glass plate 1 cm thick of refractive index 1.50 is interposed between lens and film with its plane faces parallel to film .at what distance (from lens) should object shifted to be in sharp focus on film 1.7.2 cm 2.2.4cm 3.3.2 cm 4.5.6 cm Share with your friends Share 15 Jyoti Pant answered this The shift in image position due to glass plate is given by,S=(1-1μ) t=(1-11.5)×1=13cmFor focal length of the lens,1f=1v-1u=112-1(-240)or f=24021cmNow, to get back image on the film, lens has to form image at (12-13) cm=353cm such that the glass plate will shift the image on the film.Using relation,1f=1v-1u or 1u=1v-1f1u=335-21240=-1560or u=-560 cm or -5.6 m 34 View Full Answer
