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Chapter 23
Section 1 Mirrors and Lenses
Rays and the Path of Light Waves
Because light waves travel in straight lines, you can
use an arrow called a ray to show the path and the
direction of a light wave. Rays help to show the path
of a light wave after it bounces or bends.
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Chapter 23
Section 1 Mirrors and Lenses
Mirrors and Reflection of Light
•A plane mirror is a mirror that has a flat surface.
•The reflection of an object in a plane mirror is right
side up and the same size as the object, but
reversed left to right.
• Plane mirrors form virtual images. A virtual image
is an image through which light does not travel
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Chapter 23
Section 1 Mirrors and Lenses
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Chapter 23
Section 1 Mirrors and Lenses
Mirrors and Reflection of Light, continued
•A concave mirror is a mirror that is curved inward.
• The image formed by a concave mirror depends on
the optical axis, focal point, and focal length of the
mirror.
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Chapter 23
Section 1 Mirrors and Lenses
Mirrors and Reflection of Light, continued
• A real image is an image through which light
passes.
How Images Are Formed in Concave
Mirrors
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Chapter 23
Section 1 Mirrors and Lenses
Mirrors and Reflection of Light, continued
• Convex Mirrors A convex mirror is a mirror that
curves outward.
• The image formed by a convex mirror is always
virtual, right side up, and smaller than the original
object.
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Chapter 23
Section 1 Mirrors and Lenses
Lenses and Refraction of Light
• A lens is a transparent object that forms an image
by refracting, or bending, light. Two kinds of lenses
are convex and concave.
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Chapter 23
Section 1 Mirrors and Lenses
Lenses and Refraction of Light, continued
• Convex Lenses A convex lens is thicker in the
middle than at the edges.
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Chapter 23
Section 1 Mirrors and Lenses
Lenses and Refraction of Light, continued
• Concave Lenses
A concave lens is
thinner in the
middle than at the
edges.
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Chapter 23
Section 2 Light and Sight
How You Detect Light
• Your eye gathers visible light to form the images that
you see.
• The thickness of the lens of the eye changes so that
objects at different distances can be seen in focus.
The light that forms a real image on the retina is
detected by receptors called rods and cones.
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Chapter 23
Section 2 Light and Sight
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Chapter 23
Section 2 Light and Sight
Common Vision Problems
• Nearsightedness happens when a person’s eye is
too long. A nearsighted person can see something
clearly only if it is nearby. Faraway objects look blurry.
• Farsightedness happens when a person’s eye is
too short. A farsighted person can see faraway objects
clearly. But things that are nearby look blurry.
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Chapter 23
Section 2 Light and Sight
Common Vision Problems, continued
• The images below explain how nearsightedness and
farsightedness can be corrected with glasses.
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Chapter 23
Section 2 Light and Sight
Common Vision Problems, continued
• Color Deficiency is another name for colorblindness.
The majority of people who have color deficiency can’t
tell the difference between shades of red and green or
can’t tell red from green.
• Color deficiency happens when the cones in the
retina do not work properly. Color deficiency cannot be
corrected.
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Chapter 23
Section 2 Light and Sight
Surgical Eye Correction
• Surgical eye correction works by reshaping the
patient’s cornea by using a laser. Patients often gain
perfect or nearly perfect vision after surgery.
• Risks of Surgical Eye Correction Some patients
report glares, double vision, or trouble seeing at night.
People under 20 years old should not have surgical
eye correction because their vision is still changing.
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Chapter 23
Section 3 Light and Technology
Optical Instruments
• Optical instruments are devices that use mirrors
and lenses to help people make observations.
• Cameras A camera is used to record images. All
cameras have a lens, shutter, and an aperture.
• A 35 mm camera records images on film. A digital
camera uses light sensors to record images and to
send electric signals to a computer.
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Chapter 23
Section 3 Light and Technology
Optical Instruments, continued
• Telescopes Telescopes are used to see detailed
images of large, distant objects.
•Refracting telescopes use lenses to collect light.
•Reflecting telescopes use mirrors to collect light.
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Chapter 23
Section 3 Light and Technology
Optical Instruments, continued
• Light Microscopes Microscopes are used to study
tiny, nearby objects.
• Microscopes have two convex lenses. An objective
lens is close to the object being studied. An eyepiece
lens is in the lens you look through.
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Chapter 23 Section 3 Light and Technology
Lasers and Laser Light
• A laser is a device that produces intense light of only
one wavelength and color.
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Chapter 23
Section 3 Light and Technology
Lasers and Laser Light, continued
• Uses for Lasers Lasers are used to make
holograms. A hologram is a piece of film that
produces a three-dimensional image of an object.
• Lasers have many other applications. They are used
to cut materials such as metal and cloth. Doctors
sometimes use lasers for surgery. CD players use
lasers to read CDs.
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Chapter 23 Section 3
Optical Fibers
Light and Technology
• An optical fiber is a thin, glass wire that transmits
light over long distances.
•Optical fibers are used to transmit information
through telephone cables and network computers.
Doctors use optical fibers to see inside patients’
bodies.
•Light in a Pipe Optical fibers are like pipes that carry
light. Light stays inside an optical fiber because of
total internal reflection, the complete reflection of light
along the surface of the material.
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Chapter 23
Section 3 Light and Technology
Polarized Light
• Polarized light consists of light waves that vibrate in
only one plane.
•Some sunglasses and camera lenses use polarized
filters to reduce glare.
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Chapter 23
Section 3 Light and Technology
Communication Technology
• Light waves, radio waves, and microwaves are all
types of electromagnetic waves. Cordless telephones
and cellular telephones use radio waves and
microwaves to send signals.
• Cordless Telephones The base of a cordless
telephone changes the signal it receives into radio
waves. The handset changes the radio waves into
sound.
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Chapter 23 Section 3 Light and Technology
Communication Technology, continued
• Cellular Telephones Cellular telephones send and
receives signals from distant towers. Instead of using radio
waves like cordless phones, cellular phones use microwaves
to send information.
• Satellite Technology Microwave signals are broadcast
from space to satellite dishes on Earth.
• Satellites allow more people to receive the signals and to
receive higher quality signals than if antennas on Earth were
used.
• The Global Positioning System The GPS is a network of
27 satellites that orbit Earth. A GPS receiver receives signals
from at least four satellites to find its exact location.
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