Chapter 6.1 Flashcards
light
is sometimes defined as waves of electromagnetic energy between 380 and 760 nanometers in length.
wavelength
perception of color
intensity
perception of brightness
the amount of light reaching the retinas is regulated by…
irises. Light enters through the pupils and the adjustment of the pupil size in response to changes in illumination represents a compromise between sensitivity and acuity.
sensitivity
the ability to detect the presence of dimly lit objects
acuity
the ability to see the details of objects
when illumination is high and sensitivity is not important
the pupils are constricted so the image falling on each retina is sharper and there is a greater depth of focus
when illumination is low
too low to adequately activate the receptors, the pupils dilate to let in more light, thereby sacrificing acuity and depth of focus.
behind each pupil is the lens
which focuses incoming light on the retina. lens is adjusted by the ciliary muscles.
when we focus on close objects
lens assumes its natural cylindrical shape. Increases the ability of the lens to refract (bend) light and brings close objects into sharp focus
when we focus on distant objects
the lens is flattened
accommodation
the process of adjusting the configuration of the lenses to bring images into focus on the retina
Binocular disparity
the difference in the position of the same image on the two retinas; greater for close objects than distant objects; therefore, your visual system can use the degree of binocular disparity to construct a 3-D perception from 2-D retinal images.
Movements of your eyes are coordinated
so that each point in your visual world is projected to corresponding points on your two retinas. To accomplish this, your eyes must converge (turn slightly inward). Convergence is greatest when inspecting things that are close.
