A glass slab of thickness 3cm and refractive index 1.5 is placed in front of a concave mirror of focal length 20cm. Where should a point object be placed if it is to image on to itself?

Explanation

To solve the problem step by step, we will analyze the effect of the glass slab on the position of the object and how it relates to the concave mirror.

### Step 1: Understand the effect of the glass slab
The glass slab will cause a shift in the apparent position of the point object. The shift (D) can be calculated using the formula:
\[ D = T \left(1 - \frac{1}{\nu}\right) \]
where \( T \) is the thickness of the slab and \( \nu \) is the refractive index.

### Step 2: Substitute the values into the formula
...