pls give me a detaild explanation abt sign convention for the pbm.
1)Two equiconvex lenses of focal lengths 30 cm and 70 cm,made of material of refractive index=1.5; are held in contact coaxially by a rubber band round their edges.A liquid of refractive index 1.3 is introduced in the space between the lenses filling it completely.Find the position of the image of a luminous point object placed on the axis of the combination lens at a distance of 90cm from it.
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UP 0 DOWN 0 0 1