A `20cm` thick glass slab of refractive index `1.5` is kept in front of a plane mirror. Find the position of the image (relative to mirror) as seen by an observer through the glass slab when a point object is kept in air at a distance of `40 cm` from the mirror.

Explanation

To solve the problem step by step, we need to find the position of the image as seen by an observer through the glass slab when a point object is placed in air at a distance of 40 cm from the mirror.

### Step 1: Understand the Setup
We have a plane mirror and a glass slab of thickness \( T = 20 \, \text{cm} \) and refractive index \( \mu = 1.5 \). The point object is located at a distance of \( 40 \, \text{cm} \) from the mirror.

### Step 2: Calculate the Shift Due to the Glass Slab
The effective shift in the position of the image due to the glass slab can be calculated using the formula:
\[
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