Answer: The correct answer for the fill in the blank is Bending light so that it focuses on the retina
Vision problems are mainly caused by refractive errors, which means that eye is unable to bend light rays properly on the retina causing blurred vision.
Lens is a transparent optically refracting surface, which bends light coming to it. Due to this, light is focused properly on the retina and the image of the object is seen clearly. For instance, in myopia ( person unable to see far objects), focus point is formed in front of retina and not exactly on it. By using concave lens, light rays are diverged and exactly focused on the retina. This results in the clear vision.
Thus, lenses correct vision by bending light so that it focuses on the retina.
