Exercise 7 : Question 7 (92)

What is the function of iris and the muscles connected to the lens in human eye?
Iris: When the incident light is very bright, the muscles of the iris stretch to reduce the size of the pupil. On the other hand, when the incident light is dim, the muscles of the iris relax to increase the size of pupil. Thus, the iris controls the size of the pupil and thereby amount of light entering the eye. Also, iris imparts colour to the eye. The colour of iris is different for different persons. Ciliary Muscles: Ciliary muscles adjust the focal length of the eyelens. When a distant object is to be observed, the ciliary muscles relax, so that the eye lens becomes flat. This increases the focal length of the eye lens. Hence, a sharp image of a distant object is formed on the retina. On the other hand, when a nearby object is to be observed, the ciliary muscles contract, so that the eye lens becomes round. This decreases the focal length of the eye lens. And thus a sharp image of a nearby object is formed on the retina. 2 Marks Each

What is the function of iris and the muscles connected to the lens in human eye?

Iris: When the incident light is very bright, the muscles of the iris stretch to reduce the size of the pupil. On the other hand, when the incident light is dim, the muscles of the iris relax to increase the size of pupil.
Thus, the iris controls the size of the pupil and thereby amount of light entering the eye.
Also, iris imparts colour to the eye. The colour of iris is different for different persons.
Ciliary Muscles: Ciliary muscles adjust the focal length of the eyelens.
When a distant object is to be observed, the ciliary muscles relax, so that the eye lens becomes flat. This increases the focal length of the eye lens. Hence, a sharp image of a distant object is formed on the retina.
On the other hand, when a nearby object is to be observed, the ciliary muscles contract, so that the eye lens becomes round. This decreases the focal length of the eye lens. And thus a sharp image of a nearby object is formed on the retina.
2 Marks Each