Lesson: The Human Eye and the Colourful World
What is meant by power of accommodation of the eye?
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 cannot see objects beyond 1.2 m
distinctly. What should be the type of the corrective lens used to restore
proper vision?
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.
What is the far point and near point of the human eye with
normal vision?
The near point of the eye is 25 cm.
The far point of the normal human eye is infinity.
A student has difficulty reading the blackboard while sitting
in the last row. What could be the defect the child is suffering from? How can
it be corrected?
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.