What is the transparent and protective part of the eye?

The correct answer is the cornea. The cornea is the transparent, dome-shaped surface that covers the front part of the eye. Its primary function is to shield the internal structures of the eye from dust, debris, and harmful microorganisms while also playing a crucial role in refracting light to help focus images onto the retina. The cornea is essential for good vision; any damage or irregularity can lead to significant visual impairments.

The lens, while also transparent, is located behind the iris and the cornea and primarily focuses light onto the retina, adjusting its shape to aid in seeing objects at different distances. The iris is the colored part of the eye that regulates the size of the pupil and, consequently, the amount of light entering the eye, but it is not transparent. The retina, located at the back of the eye, contains photoreceptor cells that convert light into electrical signals sent to the brain, but it does not serve as a protective outer layer like the cornea does.