Question

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

Answer 1

1w2 1exa root square

Answer 2

Thickness of glass plate (t) = 6 cm ( Given)

Distance of the object (u) = 8 cm ( Given)

Distance of the image (v) = 12 cm ( Given)

Let apparent position of the silvered surface in cm be x

Since the image is formed due to reflection at the silvered face and by the property of mirror image

Distance of object from the mirror = Distance of image from the mirror

or, x + 8 = 12 + 6 – x Þ x = 5 cm.

Therefore, refractive index of glass = Real depth/Apparent depth

                                                           = 6/5

                                                           = 1.2