there are critical periods in an infant s life that are necessary in order to have the later ability to perceive something.
WAVES Before you learn about vision and hearing, you need to understand something about waves. Both of these senses make use of different types of waves. Waves are depicted in Figure 13:
Figure 13.
The amplitude of the wave is the distance between the center point of the wave and the top of the wave. The wavelength is the distance from one wave peak to the next. The crest of the wave is the top of the wave, while the trough of the wave is the bottom of the wave. The frequency of the wave is measured in hertz and is the number of waves passing through a medium per a given time period. Hertz are usually measured in cycles per second. There is a spectrum of waves called the electromagnetic spectrum. Visible waves are just a part of this spectrum and represents those electromagnetic waves that can actually be seen by the human eye. Figure 14 shows the electromagnetic spectrum and where visible light falls:
96
