Question

8 2: physiology of vision
pathway of light through the eye and light refraction
when light passes from one substance to another substance that has a different density, its speed changes and its (1 ) are bent, or refracted. light rays are bent in the eye as they encounter the cornea, aqueous humor, lens, and vitreous humor.
the refractive, or bending, power of the cornea and humors is constant. however, that of the lens can be changed by changing its shape—that is, by making it more or less convex, so that light can be properly (2 ) on the retina. the greater the lens convexity, or bulge, the more it bends the light. the flatter the lens, the less it bends the light.
the resting eye is \set\ for distant vision. in general, light from a distant source (over 20 feet away) approaches the eye as parallel rays (figure 8 8a), and the lens does not need to change shape to focus properly on the retina. however, light from a close object tends to (3 ) and diverge, or spread out, and the lens must bulge more to make close vision possible (figure 8 8b). to achieve this, the ciliary body contracts, allowing the lens to become more convex. this ability of the eye to focus specifically for close objects (those less than 20 feet away) is called accommodation. the image formed on the (4 ) as a result of the light - bending activity of the lens is a real image—that is, it is reversed from left to right, upside down (inverted), and smaller than the object (figure 8.9, p. 288)
the normal eye is able to accommodate properly. however, vision problems occur when a (5 ) is too strong (overconverging) or too weak (underconverging) or when there are structural problems of the eyeball (as described in \a closer look\ on near - and farsightedness on p 289 - 290)
1 lens 2 rays 3 focused 4 scatter 5 retina
1 retina 2 lens 3 rays 4 focused 5 scatter
1 scatter 2 retina 3 lens 4 rays 5 focused
1 rays 2 focused 3 scatter 4 retina 5 lens
1 focused 2 scatter 3 retina 4 lens 5 rays

Explanation:

1. When light passes through different - density substances, its rays are bent. So for blank (1), "rays" is correct.
2. The lens changes shape so that light can be properly focused on the retina. So for blank (2), "focused" is correct.
3. Light from a close object tends to scatter and diverge. So for blank (3), "scatter" is correct.
4. The image is formed on the retina. So for blank (4), "retina" is correct.
5. Vision problems occur when the lens is too strong or too weak. So for blank (5), "lens" is correct.

Answer:

1. rays 2. focused 3. scatter 4. retina 5. lens