Final answer:
Contact lenses and glasses change the refraction of light rays to focus them directly onto the retina, correcting the focus of light to allow for clear vision.
Step-by-step explanation:
The answer to the student's question, "Contact lenses and glasses change the ____ of light rays to focus them directly onto the ____.", is a) Refraction; retina. This is because both glasses and contact lenses work by bending, or refracting, light rays to correct the focal point so that it falls directly on the retina, allowing for clear vision. The cornea and the lens of the eye collaborate to bend the incoming light to form a real image on the light-sensitive retina, which contains photoreceptor cells known as rods and cones that process light and send visual information to the brain via the optic nerve.
Options like reflection, dispersion, and absorption do not describe how light is manipulated by corrective lenses to focus images onto the retina. The processes of reflection and absorption do not change the path of light to focus it, and dispersion would scatter light rather than focus it.