Chapter 4 Part 2

228291450	Visible Light	electromagnetic radiation that has a wavelength of about 400 nm to about 750 nm.
228291451	Light Intensity	a physical dimension of light waves that referes to how much energy the light contains; it determines the brightness of light.
228291452	Light Wavelength	the distance between peaks in light waves.
228291453	Cornea	the curved, transparent, protective layer through which light rays enter the eye.
228291454	Pupil	an opening in the eye, just behind the cornea, through which light passes.
228291455	Iris	the colorful part of the eye, which constricts or relaxes to adjust the amount of light entering the eye.
228291456	Lens	the part of the eye behind the pupil that bends light rays, focusing them on the retina.
228291457	Retina	the surface at the back of the eye onto which the lens focuses light rays.
228291458	Accommodation	the ability of the lens to change its shape and bend light rays so that objects are in focus.
228291459	Photoreceptors	nerve cells in the retina that code light energy into neural activity.
228291460	Photopigments	chemicals in photoreceptors that respond to light and assist in converting light into neural activity.
228291461	Dark Adaptation	the increasing ability to see in the dark as time in the dark increases.
228291462	Rods	highly light-sensitive, but color-insensitive, photoreceptors in the retina that allow vision even in dim light.
228291463	Cones	photoreceptors in the retina that help us to distinguish colors.
228291464	Fovea	a region in the center of the retina where cones are highly concentrated.
228291465	Acuity	visual clarity, which is greatest in the fovea because of its large concentration of cones.
228291466	Lateral Inhibition	a process in which lateral connections allow one photoreceptor to inhibit the responsiveness of its neighbor, thus enhancing the sensation of visual contrast.
228291467	Ganglion Cells	cells in the retina that generate action potentials.
228291468	Receptive Field	the portion of the retina, and the visual world, that affects a given ganglion cell.
228291469	Optic Nerve	a bundle of fibers composed of axons of ganglion cells that carries visual information to the brain.
228291470	Blind Spot	the light-insensitive point at which axons from all of the ganglion cells converge and exit the eyeball.
228291471	Optic Chiasm	part of the bottom surface of the brain where half of each optic nerve's fibers cross over to the opposite side of the brain.
228291472	Lateral Geniculate Nucleus (LGN)	a region of the thalamus in which axons from most of the ganglion cells in the retina end and form synapses.
228291473	Primary Visual Cortex	an area at the back of the brain to which neurons in the lateral geniculate nucleus relay visual input.
228291474	Feature Detectors	cells in the cortex that respond to a specific feature of an object.
228291475	Hue	the essential "color," determined by the dominant wavelength of light.
228291476	Saturation	the purity of a color.
228291477	Brightness	the overall intensity of all of the wavelengths that make up light.
228291478	Trichromatic Theory	a theory of color vision identifying three types of visual elements, each of which is most sensitive to different wavelengths of light.
228291479	Opponent-Process Theory	a theory of color vision stating that color-sensitive visual elements are grouped into red-green blue-yellow, and black-white elements.
228291480	Synesthesia	a blending of sensory experience that causes some people to "see" sounds or "taste" colors, for example.