Transcript Ch 23 ppt: Light and Our World

Chapter 23
Light and Our World
Preview
Section 1 Mirrors and Lenses
Section 2 Light and Sight
Section 3 Light and Technology
Concept Mapping
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Chapter 23
Section 1 Mirrors and Lenses
Bellringer
What is the difference between a mirror and a lens?
What is the difference between a convex mirror and a
concave mirror? Can you think of one common use for
a convex lens and for a concave lens?
Record your responses in your science journal.
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Chapter 23
Section 1 Mirrors and Lenses
Objectives
• Use ray diagrams to show how light is reflected or
refracted.
• Compare plane mirrors, concave mirrors, and
convex mirrors.
• Use ray diagrams to show how mirrors form images.
• Describe the images formed by concave and convex
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Chapter 23
Section 1 Mirrors and Lenses
Rays and the Path of Light Waves
• A Ray of Light 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 and Reflected and Refracted Light 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
• Plane Mirrors 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
• Concave Mirrors 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
The Optical Axis, Focal Point, and Focal
Length
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Chapter 23
Section 1 Mirrors and Lenses
Mirrors and Reflection of Light, continued
• Concave Mirrors and Ray Diagrams Draw a
ray diagram to determine if a concave mirror will
form a virtual image like a plane mirror, or a real
image.
• A real image is an image through which light
passes.
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Chapter 23
Section 1 Mirrors and Lenses
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
Convex Mirror Ray Diagram
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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
How Light Passes Through Concave and Convex Lenses
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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
Bellringer
Answer the following questions in your science
journal.
What do you think a person who has colorblindness
sees? If you have colorblindness, describe what
you see.
What difficulties would a person who has
colorblindness have?
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Chapter 23
Section 2 Light and Sight
Objectives
• Identify the parts of the human eye, and describe
their functions.
• Describe three common vision problems.
• Describe surgical eye correction.
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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.
• The next slide explains how your eyes work.
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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
Bellringer
Can you describe what a laser is? List at least four
uses for lasers.
Explain your answers in your science journal.
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Chapter 23
Section 3 Light and Technology
Objectives
• Describe three optical instruments.
• Explain what laser light is, and identify uses for
lasers.
• Describe how optical fibers work.
• Explain polarized light.
• Explain how radio waves and microwaves are used
in four types of communication technology.
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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
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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
How Refracting and Reflecting Telescopes Work
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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.
•How Lasers Produce Light The word laser stands
for light amplification by stimulated emission of
radiation. Amplification is the increase in the brightness
of the light. Radiation is energy transferred as
electromagnetic waves.
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Chapter 23
Section 3 Light and Technology
Laser Light is Differs from Nonlaser Light
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Section 3 Light and Technology
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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 Light and Technology
Optical Fibers
• 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.
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Chapter 23
Section 3 Light and Technology
Optical Fibers, continued
•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
light along the surface of the material.
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Chapter 23
Section 3 Light and Technology
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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
Polarizing Filters 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.
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Chapter 23
Section 3 Light and Technology
Communication technology, continued
• 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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Chapter 23
Section 3 Light and Technology
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Chapter 23
Light and Our World
Concept Mapping
Use the terms below to complete the Concept
Mapping on the next slide.
real
convex
light
lenses
virtual
mirrors
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Chapter 23
Light and Our World
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Chapter 23
Light and Our World
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