(a) Myopia is the defect of the eye vision due to which a person can see the near by objects clearly but cannot see the far objects so distinctly.
Causes of myopia: Myopia is caused:
-due to the elongation of the eyeball.
-due to decrease in the focal length of the eye lens.
Myopia can be corrected by using a concave lens of suitable focal length in the spectacles of such a person.
(b)The ability of the eye lens to adjust its focal length is called automatic accommodation. However, the focal length of the eve lens cannot be decreased below a certain limit. The maximurn accommodation of a normal eye is reached when the object is at a distance of 25 cm from the eyes. Thus, the normal eye is unable to focus an object placed within 10 cm from the eye because all the power of accommodation has already taken place.
