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Asked in NEET 2023 Manipur · Lens maker's formula and power
Given: a converging lens whose three layers are three different transparent media, and a point object O on the axis beyond 2f.
Idea: refraction at a surface depends on the refractive index, so each layer acts as a separate thin lens that happens to share the same pair of surfaces.
1/f=(μ-1)(1/(R₁)-1/(R₂)) gives a different f for each of the three values of μ.
For every one of those focal lengths the object lies beyond 2f, so every layer forms a real image, and the three images sit at three different points on the axis.
So 3 real images are obtained.
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