The basic function of the eye is often compared to a simple camera.
Light travels in straight lines but bends when it hits another transparent medium.
The cornea is the curved front surface of the eye. When a ray of light hits this curved surface, it bends. It is here that most of the refraction occurs. The refractive index is approximately 1.376, which is comparable to that of glass or plastic. The iris is the coloured part of the eye.