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Chapter 3 Lenses
as it passes through an object is known as
refraction. The principle of refraction makes
it possible to design lenses that can make an
object appear larger or smaller.
The Pinhole Camera
A simple pinhole camera can make pho-
tographs without a lens. See Figure 3-5. Light
refl ected from the subject enters through
the pinhole. It travels through the empty
space inside the camera to form an image on
the fi lm. The tiny pinhole allows light rays
to travel in a straight line from the subject
being photographed to the fi lm. An inverted
(upside-down) image strikes the fi lm. See
Figure 3-6.
If the pinhole is made larger it admits
more light, but rays passing through the pin-
hole scatter. The resulting image is not very
sharp. Figure 3-7 shows photographs taken
with a pinhole camera.
Such cameras are not very practical for
general photography. The results are poor,
Figure 3-3. Light rays usually travel in straight lines,
but they are not always traveling parallel to one
another.
Figure 3-4. Light rays can be transmitted, absorbed,
and refl ected.
Figure 3-5. These pinhole cameras can make photographs without using a lens.
Light rays
Light source
Reflected
rays
Absorbed
rays
Transmitted
rays
Incident light