Question

A glass slab of thickness t = 3 cm, R.I. 2 3   is placed between the object O and the concave mirror of focal length f = 4.5 cm. It is observed that the image is formed at the object. If we withdraw the slab, the image will be formed at a distance of

Answer 1

Apparent shift = \(t(1 -x)\)

\(= 3(1 - \frac 23)\)

\(= 1 cm\)

therefore, 

\(x - 1 = 2 \times 4.5\)

\(x = 9 + 1\)

\(x = 10 cm\)

so,

\(\frac 1v - \frac 1x = \frac {-2}9\)

\(\frac 1v - \frac 1{10} = \frac {-2}9\)

\(v= \frac{90}{11} cm\)