Psych module 18 vision and perceptual organization and interpretation. Wavelength-the distance from the peak of one light or sound wave to the peak of the next. Electromagnetic wavelengths vary from the short blips of cosmic rays to the long pulses of radio transmission. Hue-the dimension of colour that is determined by wavelength of light; what we know as the colour names blue, green, and so forth. Intensity-the amount of energy in a light or sound wave, which we perceive as brightness or loudness, at determined by the wave"s amplitude. Pupil-the adjustable opening in the center of the eye through which light enters. Iris- a ring of muscle tissue that forms the coloured portion of the eye around the pupil and controls the size of the pupil opening. Lens-the transparent structure behind the pupil that changes shape to help focus images on the retina.