(a) The three ascending steps of conscious experience are.
(b) Sensation refers to the.
Answers: (a) sensation, perception, and cognition; (b) raw data of experience.
Vision: Seeing Is Believing
Most people think of vision as the primary sense. We need to see in order to drive,
to read, to look at the people we love, and so forth. If asked what sense they con-
sider the most important, most students in an introductory psychology class
answer that it is vision.
In order to appreciate the visual process it is necessary first to give some atten-
tion to the stimulus that makes it possible. That stimulus is light. From the point
of view of physics, there are two ways to look at light. It can be said that light con-
sists of a set of electromagnetic waves. Or it can be said that light consists of a
stream of particles, or quanta, called photons.In either case, light travels at the
same speed—about 186,000 miles per second. For the purposes of psychology, we
will limit our description of light to the electromagnetic wave theory.
An electromagnetic wave,consisting of a system of electrical and magnetic
fields, is a unique kind of wave. It can even travel through a vacuum—without a
medium to carry it. Otherwise, communication with voyagers to the Moon or
with distant space probes would not be possible. Radio waves are one kind of
electromagnetic wave.
(a) If light is looked upon as a stream of particles, or quanta, what are the particles
called?
(b) A unique property of an electromagnetic wave is its ability to travel through
.
Answers: (a) Photons; (b) a vacuum.
The waves to which we give the name “light” are a narrow band of the elec-
tromagnetic spectrum. This spectrum ranges from relatively “long” radio
waves at one end of the spectrum to relatively “short” gamma rays at the other
end. In between the extremes we find the light waves. These range in length,
measured crest to crest, from 750 nanometers to 400 nanometers. (A nanometer
is one billionth of a meter.) The part of the electromagnetic spectrum we can see
is called the visible spectrum.The principal colors of the visible spectrum, also
known as the rainbow, starting at 750 nanometers, are red, orange, yellow, green,
blue, indigo, and violet. The colors always appear in the same order either in a
rainbow or when white light is broken up by a prism.
Sensation: Studying the Gateways of Experience 47
