Chapter 11 Sound and Light

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Chapter 11 Sound and Light

• Beginning on page 35 of your packet.

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Section 1 Sound

• A. Sound waves form when a vibrating object
  collides with air (or any kind of) molecules
  transferring energy to them.

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Section 1 Sound

• 1. Compressional waves have two regions, called
  compressions and rarefactions, which push air
  molecules together and then spread them apart.

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Compressional Wave
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Section 1 Sound

• A sound waves speed depends on the temperature
  and state of the medium.
• 1. Sound travels more quickly through solids and
  liquids the molecules are closer together than
  those in gas.

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Section 1 Sound

1. 2. As a mediums temperature rises, its
   molecules move faster, conducting sound waves
   faster.

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Section 1 Sound

• C. The amount of energy a wave carries
  corresponds to its amplitude, which is related to
  the density of the particles in the compressions
  and rarefactions.

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Section 1 Sound

• D. Intensity the amount of energy that flows
  through a certain area in a specific amount of
  time.

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Section 1 Sound

1. Loudness human perception of sound intensity.
2. Each unit on a scale that measures sound
   intensity is a decibel.

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Section 1 Sound

• Pitch how low or high a sound seems to be (dog
  whistler)
• Frequency is the number of compressions or
  rarefactions of a sound wave that pass per
  second humans can hear 20-20K

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Section 1 Sound

1. Ultrasonic waves have sound frequencies over
   20,000 Hz that have medical and other uses.
2. Subsonic waves with f below 20 Hz rumble

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Section 1 Sound

• F. Doppler effect change in pitch or wave
  frequency due to a moving wave source (or to the
  movement of the listener).

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Section 1 Sound

• G. Echolocation process of locating objects by
  sending out sounds and interpreting the waves
  reflected back. Where might you find this in
  nature?

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Section 1 Sound

1. Sonar a system that uses the reflection of
   underwater sound waves to locate objects.
2. Ultrasound waves are used in medicine to
   diagnose, monitor, and treat many conditions.

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Escape
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Section 2 Reflection and Refraction of Light

• Light and matter objects must reflect light to
  be seen.
• 1. Opaque materials do not allow light to pass
  through them they only absorb and reflect light.

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Section 2 Reflection and Refraction of Light

1. Some light passes through translucent materials
   (like the light coverings in D-5).
2. Transparent materials transmit all light,
   absorbing and reflecting little light.

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Section 2 Reflection and Refraction of Light

• Law of reflection the angle at which light
  strikes a surface equals the angle at which it is
  reflected.
• 1. Regular reflection-reflection of light waves
  from a smooth surface.

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Section 2 Reflection and Refraction of Light

1. Diffuse reflection-reflection of light waves in
   many directions from a rough surface.
2. Scattering-type of diffuse reflection that occurs
   when light waves traveling in one direction are
   made to travel in many different directions.

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Section 2 Reflection and Refraction of Light

• Refraction of light-change in the speed of light
  wave when it passes from one material to another.
• 1. The index of refraction indicates how much a
  material reduces the speed of light the more the
  light is slowed, the greater the index of
  refraction.

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Section 2 Reflection and Refraction of Light

1. Prisms separate white light into visible spectrum
   based on light wavelengths.
2. Refraction of light through air layers of
   different densities can result in a mirage.

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Section 2 Reflection and Refraction of Light

• Discussion question Why cant you see an object
  in the dark?

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Section 2 Reflection and Refraction of Light

• Discussion question Why cant you see an object
  in the dark?
• Answer Objects must reflect light to be seen.

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Section 3 Mirrors, Lenses and the Eye

1. Light waves spread in all directions from a
   light.
2. Mirror any surface that produces a regular
   reflection.

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Section 3 Mirrors, Lenses and the Eye

1. Plane mirror flat, smooth mirror in which an
   image appears upright.
2. In a concave mirror, the mirror surface is curved
   inward the image depends on location of object
   relative to focal point.

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Section 3 Mirrors, Lenses and the Eye

• Convex mirrors are curved outward, diverge light
  rays when reflected, and show virtual images.
• C. Lens transparent material with a curved
  surface that refracts light rays.

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Section 3 Mirrors, Lenses and the Eye

• A convex lens is thicker in the middle than at
  the edges.
• a. Form real, reduced, and inverted image when
  object is more than two focal lengths from the
  lens.

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Section 3 Mirrors, Lenses and the Eye

1. Form real, enlarged, and inverted image when
   object is between one and two focal lengths from
   the lens.
2. Form virtual, enlarged, and upright image when
   object is less than one focal length from the
   lens.

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Section 3 Mirrors, Lenses and the Eye

• A concave lens is thinner in the middle and
  thicker at the edges.
• D. The structure of your eye allows you to focus
  on objects.

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Section 3 Mirrors, Lenses and the Eye

1. Light enters the eye through the cornea, a
   transparent covering on the eyeball.
2. A convex lens helps to focus light rays to form
   sharp images.

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Section 3 Mirrors, Lenses and the Eye

• Retina inner lining of the eye that converts
  light into electrical signals that the brain
  interprets.
• E. Vision problems occur when lenses in the eye
  do not focus images properly.

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Section 3 Mirrors, Lenses and the Eye

1. Farsightedness when lens is not curved enough
   to form an image of close objects.
2. Astigmatism the corneas surface is unevenly
   curved.

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Section 3 Mirrors, Lenses and the Eye

• 3. Nearsightedness lens does not flatten
  enough to form an image of distant objects.

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Section 3 Mirrors, Lenses and the Eye

• Discussion Question!
• What are three shapes of mirrors?

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Section 3 Mirrors, Lenses and the Eye

• Discussion Question!
• What are three shapes of mirrors?
• Answer Plane (flat), concave (curved inward)
  and convex (curved outward).

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This Time
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Section 4 Light and Color

• A. Color is determined by the wavelength of
  light an object reflects.
• 1. Objects appear to be white because they
  reflect all colors of visible light.

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Section 4 Light and Color

• 2. Objects appear to be black because they
  absorb all colors of visible light.

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Section 4 Light and Color

• 3. Filter transparent material that absorbs
  all colors except the one it transmits.

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Cool Science Explanation.

• Can you explain why the image of the Sun appears
  reddish at sunrise and sunset?

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The Sun

• The sunlight has to travel through more
  atmosphere at dawn and dusk.
• The atmosphere refracts more light at these times.

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Section 4 Light and Color

• Light enters the eye and is focused on the
  retina, which absorbs light.
• 1. Cone cells distinguish colors and detailed
  shapes most effective in daytime vision.

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• While humans have three types of color-detecting
  cells, mice and most other mammals have just two.
  But when a group of scientists gave mice the
  human gene for a third color detector, they were
  able to detect colors that no mouse has ever seen
  before.

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Section 4 Light and Color

1. Rod cells sensitive to dim light most
   effective in nighttime vision.
2. Color blindness results when one or more sets of
   cones do not function properly.

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Section 4 Light and Color

• All colors of light are made by mixing the three
  primary colors of red, green, and blue.
• 1. Primary colors of light are additive and
  combine to form white light.

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Section 4 Light and Color

• Pigment colored material that absorbs some
  wavelengths of light and reflects others.
• 1. Primary colors of pigment are magenta, cyan
  and yellow.

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Section 4 Light and Color

• 2. Primary colors of pigment are subtractive and
  combine to form black.

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Section 4 Light and Color

• Discussion Question What would happen if none
  of the cones in a persons eye worked properly?

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Section 4 Light and Color

• Discussion Question What would happen if none
  of the cones in a persons eye worked properly?
• Answer The person would not see color.

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Now, to see if YOU are colorblind

• In your notes, write down the numbers, letters or
  symbols you see in the next slides.
• Please, no talking or peeking.

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The End!