A certain person can see clearly objects lying between `20 cm and 250 cm` from his eye. What spectacles are required to enable him to see distant objects clearly ? When he is wearing these spectacles, what is his least distance of distinct vision ?

Explanation

To solve the problem step by step, we need to determine the type of spectacles required for the person to see distant objects clearly and then find out the least distance of distinct vision while wearing those spectacles.

### Step 1: Identify the current vision range
The person can see clearly between 20 cm (near point) and 250 cm (far point). This means that the person has a limited range of vision and cannot see objects beyond 250 cm clearly.

### Step 2: Determine the requirement for distant vision
Distant objects are considered to be at infinity. To enable the person to see distant objects clearly, we need to bring the far point of his vision (250 cm) to infinity. This requires the use of a lens.

...