An object O is placed at 8 cm in front of a glass
slab, whose one face is silvered .
The thickness of the slab 9 cm. If the image is
formed 10 cm behind silvered face, the refractive
index of the glass is
(1) 1.63 (2) 1.3
(3) 1.4 (4) 1.2

Image formed by the first transparent surface:I1 = 8×μ+9where μ is the refractive index of the material.image formed by the reflection from the silvered surface is I2I2 = 8μ+thickness of the slab = 8×μ + 9behind the mirrornow final image will be at 10 cm10 = 8μ+9μ10μ = 8μ+92μ = 9μ = 4.5

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