Light and Optics

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Light and Optics
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• Light
• We see objects because of their reflected light.
• Can carry heat
• Travels far and fast
• Travels in a straight line unless bent or
  reflected.
• Can carry color.

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• What makes light?
• Almost everything that creates light is made of
  atoms.
• Elements have electrons which are in shells.
• The further from the nucleus, the more energy it
  has.
• As it falls to a lower level, emits energy.

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• Visible Light and UV
• ROY G. BIV-colors of visible light.
• Sunlight emits UV along with other rays.
• Gives us Vitamin D
• Too much harmful.
• Most filtered by ozone.

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• Speed of Light
• Speed of sound-340 m/s
• Speed of light-300 million m/s
• Einstein figured out how light behaved

• Polarization
• Rays are all vibrating on the same plane.
• A polarizer allows only 1 type through. Ex
  sunglasses.
• Many things use polarized light-laptop monitors

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• Color
• Color has freq and wavelength
• One goes up, the other goes down.
• Red-longest wavelength, lowest freq
• Violet-shortest wavelength, highest freq

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• How do I see color?
• Photochemical receptors receive the light (rods
  and cones)
• They release a chemical signal to the brain.
• Brain interprets the signal
• Rods-brightness, cones-the color
• Primary colors of light red, blue, green mix
  together to make white.

• Additive and subtractive
• Primary colors of light are additive-each one
  adds more light and the result is white.
• Primary pigment colors are subtractive-each one
  takes away more light and the result is black.
  (magenta, cyan, yellow)

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Optics and Reflection

• Law of reflection determines the reflected ray
• Light rays bounce off a mirror at the same angle
  at which they arrive
• We always define angles relative to the normal
  (the line perpendicular to the mirror (or lens)

• Optics-the study of how light behaves
• Deals with the collection and use of light to
  create images
• Includes lenses, mirrors, and prisms

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Mirrors Prisms

• Mirrors reflect light
• Flat mirrors show true-size
• Curved mirrors cause light to come together or
  spread apart
• Prisms cause light to change directions
• Traditionally used to separate the colors of
  light and to show how light bends

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Images

• Objects are any real physical things that gives
  off or reflects light
• Images are pictures of objects formed where
  light rays from the object meet
• Normally light travels in straight lines
• To make images, sometimes light must be bent
  between an object and your eye

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Reflection Mirrors

• A mirror reflects rays of light so that they
  change their path
• Mirrors create a virtual image
• Image appears behind the mirror and is reversed
• The light rays are reflected back to your eye at
  an equal but opposite angle
• Incident ray the ray that comes from the object
  and hits the mirror
• Reflected ray the ray that bounces off the
  mirror

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Refraction and Lenses

• A lens uses refraction to cause light to come
  together or spread apart
• Refraction The bending of light that occurs
  when light crosses a boundary between two
  different substances
• EX. Glass, Plastic, Water
• Lens a shape of transparent material that is
  used to bend the light rays
• Shape is determined by how strong we bend the
  light

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Focal Point Focal Length

• Focal point the point at which light rays meet
  after having entered a converging lens parallel
  to the principal axis.
• Focal length - the distance from the center of
  the lens to the focal point

• Where is the focal point in this eye diagram?
• Where is the focal length?

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Lens Types

• Converging lenses bend parallel light rays
  passing through them inward toward the focal
  point
• Diverging lenses bend the parallel light rays
  passing through them outward away from the focal
  point

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Kinds of Images

• Real images
• can be projected on a smooth surface by lenses
• Inverted
• Virtual images
• Appear to be coming from an object larger and
  farther away than the real object
• Mirrors and lenses create virtual image

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The Eye

• Know the parts of the eye
• Lens, cornea, iris, retina optic nerve

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Lens

• The lens can change its shape to focus at
  different distances.
• A lens that focuses in front of the retina is a
  condition called myopia (near sightedness)- need
  concave lens
• A lens that focuses objects behind the retina is
  a condition called hyperopia (far
  sightedness)-convex lens

Long Focal Length
Use Converging Lens Thick in center than on the
sides (Convex)
Use Diverging Lens Thicker on sides than in
center. (Concave)
Short Focal Length