CSET Practice Test on Waves

Each individual wavelength within the spectrum of visible
light wavelengths is representative of a particular color.
When light of that particular wavelength strikes the
retina of our eye, we perceive that specific color
sensation. Isaac Newton showed that light shining through
a prism will be separated into its different wavelengths
and will thus show the various colors that visible light
is comprised of. The separation of visible light into its
different colors is known as dispersion. Each color is
characteristic of a distinct wavelength; and different
wavelengths of light waves will bend varying amounts upon
passage through a prism; for these reasons, visible light
is dispersed upon passage through a prism. Dispersion of
visible light produces the colors red (R), orange (O),
yellow (Y), green (G), blue (B), indigo (I), and violet
(V). It is because of this that visible light is sometimes
referred to as ROY G. BIV. The red wavelengths of light
are the longer wavelengths and the violet wavelengths of
light are the shorter wavelengths. The visible light
spectrum is shown in the diagram to the left.

When all the wavelengths of the visible light spectrum
strike your eye at the same time, white is perceived.
Thus, visible light is sometimes referred to as white
light.  White is not a color at all, but rather the
combination of all the colors of the visible light
spectrum. Likewise, black is not actually a color. Black
is merely the absence of the wavelengths of the visible
light spectrum.

When a ray of light strikes a plane mirror, the light ray
reflects off the mirror. Reflection involves a change in
direction of the light ray. The convention used to express
the direction of a light ray is to indicate the angle
which the light ray makes with a normal drawn to the
surface of the mirror. The angle of incidence is the angle
between this normal and the incident ray; the angle of
reflection is the angle between this normal and the
reflected ray. According to the law of reflection, the
angle of incidence equals the angle of reflection.