An observer looks at an object kept at a distance 30 cm in air. If a rectangular glass plate (`mu` =1.5) is placed between the observer and the object with its thick-ness along the line of observation, the object appears to the observer to be at a distance 25 cm. Find the thickness of glass plate. Position of the glass plate is now shifted (i) from object towards observers (ii) from observer towards the object How does it change the apparent position of the object as seen by the observer?

Explanation

To solve the problem, we need to find the thickness of the glass plate and analyze how shifting its position affects the apparent position of the object.

### Step 1: Understand the Shift in Apparent Position
When the observer looks at the object through the glass plate, the object appears to be at a different distance due to the refraction of light. The apparent position of the object is given as 25 cm when the actual distance is 30 cm. The shift in the apparent position can be calculated as:

\[ \text{Shift} (S) = \text{Actual Distance} - \text{Apparent Distance} = 30 \, \text{cm} - 25 \, \text{cm} = 5 \, \text{cm} \]
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