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Unformatted text preview: CHAPTER 4 LEARNING OBJECTIVES When you have mastered the material in this chapter, you should be able to do the following: 1. List the three properties of light and the aspects of visual perception that they influence.-Light is a form of electromagnetic radiation that travels as a wave, moving, naturally enough, at the speed of light.-Light waves vary in amplitude (height) and wavelength (the distance between peaks). Amplitude affects mainly the perception of brightness. Wavelength affects mainly the perception of color. The lights humans see normally are mixtures of different wavelengths. Light can also vary in purity (how varied the mix is). Purity influences perception of the saturation, or richness of colors. Most objects do not emit light, they reflect it (sun, lamps, fireflies). What most people call light includes only the wavelengths that humans can see. The visible spectrum is only a slim portion of the total range of wavelengths. Vision is a filter that permits people to sense only a fraction of the real world. Many insects can see shorter wavelengths than humans, in the ultraviolet spectrum, fish and reptiles can see longer wavelengths, in the infrared spectrum. Incoming visual input must be converted into neural impulses that are sent to the brain. 2. Describe the role of the lens and pupil in the functioning of the eye.- The eye serves 2 main purposes: they channel light to the neural tissue that it receives, called the retina, and they house that tissue. Light enters the eye through the front at the cornea. The cornea and the lens (behind it) form an upside down image of objects on the retina and adjust the focus of the image.- The lens is a transparent eye structure that focuses the light rays falling on the retina. It is made up of soft tissue, capable of adjustments that do a process called accommodation- occurs when the curvature of the lens adjusts to alter visual focus. When you focus of a close object, the lens gets fatter in order to give a clear image, the lens flattens when focused on distant objects. Nearsightedness- close objects are clear, distant are blurry usually because the eyeball is too long and the focus of light on distant objects fall short of the retina, or when the cornea or lens bends too much light. Farsightedness- distant objects are seen clearly but close are blurry because the focus of light falls behind the retina, this occurs when the eyeball is too short. Cataract- a lens that is clouded.- The pupil is the black center of the eye or the opening in the center of the iris that helps regulate the amount of light passing into the rear chamber of the eye. When the pupil constricts, it lets less light into the eye which sharpens the image and when the pupil dilates (opens) it lets more light in making the image less sharp. In bright light the pupils constrict to take advantage of the sharpened image, in dim light they dilate. Image sharpness is sacrificed to allow more light to fall on the retina so that more remains they dilate....
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This test prep was uploaded on 04/20/2008 for the course PSYC 401 taught by Professor Michaelmangan during the Spring '08 term at New Hampshire.
- Spring '08