Question

The function of the iris is to
A. Move lens forward and backward
B. Refract light rays
C. Bring about movements of eyelids
D. Alter the size of the pupil

Answer 1

Hint:- The eye is a sensory organ present in humans on either side of the face, where it has a
the visible part and the part that is present in the sac of orbit, in the visible part, eye structure the white outer coat is called the sclera, where the colored part is called iris.

Complete step-by-step solution:-
1. An eye senses the light and it is the sensory organ that has a connection with the brain and
provides us vision, where different parts of the eye have different functions.
2. The eye contains the structure called the cornea, it is called a front window of the eye, where
The function is to transmit and focus the light that enters the eye.
3. And the colored part of the visible structure of the eye is the iris, when there is more amount of
light, it closes the pupil to reduce the intensity of light, while whenever there is low light, it
opens up the pupil more to allow the extra intensity of light, so they maintain of iris in the eye is
to alter the size of the pupil according to the entry of light.
4. Eyes are always working like a camera, where the camera opens or closed the shutter when it
requires the light or depends on the amount of light required, similarly, the iris and pupil of the
eyes control the amount of light entry to the eye.
So the correct option is D.

Note:- Among all structures of the eye, the iris is a highly pigmented part, where the color of eyes depends on this structure and it may be brown, black, hazel, grey, etc and in the eye, the pupil is the eye aperture, where iris is considered as the diaphragm.