Light and Our World

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Light and Our World
Chapter 23
Preview
Section 1 Mirrors and Lenses Section 2 Light
and Sight Section 3 Light and Technology
Concept Mapping
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Section 1 Mirrors and Lenses
Chapter 23
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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Section 1 Mirrors and Lenses
Chapter 23
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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Section 1 Mirrors and Lenses
Chapter 23
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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Section 1 Mirrors and Lenses
Chapter 23
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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Section 1 Mirrors and Lenses
Chapter 23
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Section 1 Mirrors and Lenses
Chapter 23
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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Section 1 Mirrors and Lenses
Chapter 23
The Optical Axis, Focal Point, and Focal Length
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Section 1 Mirrors and Lenses
Chapter 23
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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Section 1 Mirrors and Lenses
Chapter 23
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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Section 1 Mirrors and Lenses
Chapter 23
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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Section 1 Mirrors and Lenses
Chapter 23
Lenses and Refraction of Light, continued

• Convex Lenses A convex lens is thicker in the
  middle than at the edges.

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Section 1 Mirrors and Lenses
Chapter 23
Lenses and Refraction of Light, continued

• Concave Lenses A concave lens is thinner in the
  middle than at the edges.

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Section 2 Light and Sight
Chapter 23
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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Section 2 Light and Sight
Chapter 23
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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Section 2 Light and Sight
Chapter 23
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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Section 2 Light and Sight
Chapter 23
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Section 2 Light and Sight
Chapter 23
Common Vision Problems

• Nearsightedness happens when a persons eye is
  too long. A nearsighted person can see something
  clearly only if it is nearby. Faraway objects
  look blurry.
• Farsightedness happens when a persons eye is
  too short. A farsighted person can see faraway
  objects clearly. But things that are nearby look
  blurry.

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Section 2 Light and Sight
Chapter 23
Common Vision Problems, continued

• The images below explain how nearsightedness and
  farsightedness can be corrected with glasses.

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Section 2 Light and Sight
Chapter 23
Common Vision Problems, continued

• Color Deficiency is another name for
  colorblindness. The majority of people who have
  color deficiency cant tell the difference
  between shades of red and green or cant 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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Section 2 Light and Sight
Chapter 23
Surgical Eye Correction

• Surgical eye correction works by reshaping the
  patients 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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Section 3 Light and Technology
Chapter 23
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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Section 3 Light and Technology
Chapter 23
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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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Section 3 Light and Technology
Chapter 23
How Refracting and Reflecting Telescopes Work
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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.
• 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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Section 3 Light and Technology
Chapter 23
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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Section 3 Light and Technology
Chapter 23
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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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Section 3 Light and Technology
Chapter 23
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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Section 3 Light and Technology
Chapter 23
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Light and Our World
Chapter 23
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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Light and Our World
Chapter 23
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Light and Our World
Chapter 23