The specimen is the focal point, which is the place where all the reflected
light originates. Light travels in a straight line from the focal point to the lens
where the light is bent in a process called refraction. The angle at which light
is bent is called the angle of refraction, which is measured in degrees from the
natural path of the light. The degree of angle of refractionis determined by
the curvature in the lens. The more the lens curves, the greater the angle of
refraction.
The image appears larger as the light reflected from the image is refracted.
Although the image appears magnified, curvature does distort the image. The
amount of distortion depends on the angle of refraction and the distance between
the lens and the specimen, which is called the focal length. The point at which
light rays meet is called the focal point(Fig. 3-3).
CHAPTER 3 Observing Microorganisms^53
Fig. 3-2. Convex lens.Focal PointFocal Length
Fig. 3-3. The focal point is where light rays meet.