Question

Near point of human eye is
(a) 25cm
(b) 20cm
(c) 15cm
(d) 10cm

Answer 1

Hint: The near point of the eye is defined as the minimum distance at which a normal eye can see the objects clearly without any strain. The minimum distance at which a human eye can see clearly without strain or the near point is close to 1 foot.

Complete step by step answer:
The human eye can see objects clearly without any strain on the eye when an object is placed at least 25 cm away. This distance of 25 cm is known as the near point of the eye. When the object is placed at a distance between 25 cm and infinity, the image of the object is formed on the retina and interpreted clearly. If an object is placed closer than 25 cm, an image is formed behind the retina and hence strains the eye and is not clear.

Additional Information:
The near point may sometimes vary because of certain conditions of the eye called myopia and hypermetropia.

For example: In a myopic eye, the near point is closer than the average distance whereas in hypermetropia the near point is further away.
So, the answer is, “25cm”.

Note:
- This near point can sometimes be written in the form of power or dioptres. 1D or 1 dioptre = $\frac { 1 }{ 1metre }$ So near point is $\frac { 1 }{ 25 cm }$ =$\frac { 1 }{ 0.25 m }$ =${ 4D }$
- The human eye can adjust according to the distance of the object from the eye to look at the objects. - This is called the power of accommodation. - The ciliary muscles adjust the diameter of the lens to achieve this.