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 find the position of the image as seen by an observer through a glass slab in front of a plane mirror, we can follow these steps:

### Step 1: Understand the setup
We have a plane mirror and a glass slab of thickness 20 cm and refractive index 1.5 placed in front of it. A point object is located in air at a distance of 40 cm from the mirror.

### Step 2: Calculate the shift due to the glass slab
The effective shift caused by the glass slab can be calculated using the formula:
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