Explain the function of main parts of an eye by drawing a simple sketch of it.

The function of the main parts of an eye is:

1. Iris: The muscular diaphragm behind the cornea that controls the amount of light that enters the eye.

2. Pupil: The aperture of an eye behind the cornea whose size can be controlled by the iris.

3. Ciliary muscles: The muscular structures that hold the eye lens in its position and also control their aperture.

4. Retina: It is a light-sensitive tissue where the image is formed after refraction.

Fig. Structure of eye