Question

The least distance of distinct vision for a normal person is about:
A. $0.01m$
B. $0.5m$
C. $0.25m$
D. $25m$

Answer 1

Hint: Humans are capable to see within a wide range of distances. Although, a healthy person can see as far as possible but if the object is moved towards the individual, he is not able to see it clearly after a fixed point. The image doesn’t appear to be clear.

Complete step-by-step answer:
Least distance of distinct vision, also called LDDV, is the distance of the nearest point from the eye of a healthy individual with a ‘normal’ vision. It is the nearest distance at which when an object is kept, it can be clearly seen by an individual having a ‘normal ’ vision.
An individual is said to have a normal vision if he has 20/20 vision. If you have 20/20 vision, it means that you are able to see an object, placed 20 metres away from you, in the same way as seen by a normal person.
A healthy individual having ‘normal’ vision has a Least distance of distinct vision of $25cm$ or $0.25m$.

So, the correct answer is “Option C”.

Additional Information: If the least distance of distinct vision of a person is not $25cm$, it can be corrected using an appropriate lens, either concave or convex. Human eyes are capable of focusing more than 5 objects per second. Human eyes create the image of every object inverted, i.e. upside down. It is the brain which converts these images upright and hence you see the normal image of the object. Our eyes are the only body part which remains of the same size from birth. It does not grow. If compared with a camera, human eyes have more than 500 megapixels!

Note: As one grows old, the eyes of the person also becomes weak. With increase in age, the flexibility of the lens of eyes to focus on objects at different distances, decreases. As a result, the least distance of distinct vision also changes.