Lesson: The Human Eye and the Colourful World
Ciliary muscles present in the eye helps in changing the focal length of the eye lens. This enables the eye to focus on both near and distant objects. The ability of the eye to focus both near and distant objects, by adjusting its focal length, is called the accommodation of the eye.
A person with a myopic eye should use a concave lens to restore proper vision.
The focal length of the concave lens should be of 1.2 m.
The near point of the eye is 25 cm.
The far point of the normal human eye is infinity.
As the student is unable to see the letters written on the board, it is a case of myopia (near-sightedness). The doctor would advise the student to use a concave lens of appropriate power to enable him to see distant objects clearly.