![]() Light enters the eye through the cornea, which is a clear covering that protects the eye and begins to focus the incoming light (see Figure 5.5). The sensing eye and the perceiving visual cortex Our eyes detect only the range from about 400 to 700 billionths of a metre as such, this part of the electromagnetic spectrum is known as the visible spectrum. Humans are blind to almost all of this energy. Electromagnetic waves vary in their wavelength - which is the distance between one wave peak and the next wave peak - with the shortest gamma waves being only a fraction of a millimetre in length and the longest radio waves being hundreds of kilometres long. The air around us is filled with a sea of electromagnetic energy: pulses of energy waves that can carry information from place to place. ![]() Once this visual information reaches the visual cortex, it is processed by a variety of neurons that detect colours, shapes, and motion, and that create meaningful perceptions out of the incoming stimuli. Seeing begins when light falls on the eyes, initiating the process of transduction. A significant part of our cerebral cortex is devoted to seeing, and we have substantial visual skills. Whereas other animals rely primarily on hearing, smell, or touch to understand the world around them, human beings rely in large part on vision.
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