Light Waves

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Light Waves

• Sec 1

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Light Waves Strike objects

• Reflected
• Absorbed
• Transmitted

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Properties of objects

• Opaque
• Transparent
• Translucent

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Opaque

• A material that reflects or absorbs all of the
  light that strikes it.

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Transparent

• Material transmits light
• Light passes through allowing you to see what is
  on the other side

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Translucent

• Some light passes through
• Material scatters light as the light passes
  through
• You cannot see details

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Reflection

• Two kinds of wave reflection
• Regular and
• Diffused

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Regular Reflection

• Occurs when parallel rays of light hit a smooth
  surface
• All the rays are reflected at the same angel

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Diffuse Reflection

• When parallel rays of light hit a bumpy, or
  uneven surface
• The rays are reflected at different angels

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Mirrors

• Sheet of glass
• Smooth, silver-colored coating
• When light passes through the mirror, the back
  coating causes the light to reflect regularly,
  allowing you to see an image

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Image

• Is a copy of an object formed by reflected or
  refracted rays of light

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Plane Mirror

• Flat mirror
• Produces a image that is right-side up and
• The same size as the object being reflected

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Virtual Image

• The image you see when you look in a plane mirror
  is a virtual image
• Right-side up or upright

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Concave Mirrors

• Surface curves inward
• Can form virtual images, real images, or no image
• Depends on position of the object in relation to
  the focal point

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Real Image

• Formed when rays actually meet at a point
• The images are upside down, or inverted

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Focal Point

• The point at which the rays meet

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Convex Mirrors

• A mirror with a surface that curves outward
• Images are always virtual

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Refraction and Lenses

• Sec 2

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Index of refraction

• measure of how much a ray of light bends when it
  enters that material

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Mirages

• Is an image of a distant object caused by
  refraction of light
• Page 245

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Concave lens

• Is thinner in the center than at the edges

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Convex lenses

• Is thicker in the center than at the edges

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Color

• Sec 3

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Color

• The color of an object is the color of light it
  reflects
• Whitereflects all colors
• Black absorbs all colors

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Primary Colors

• Three colors that can be used to make any other
  color
• Red, green, and blue
• Any two primary combined in equal amounts produce
  a secondary color

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Seeing Light Waves

• Sec 4

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The Eye

• Organ System
• Each part plays an important part in helping you
  see

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Cornea

• Light enter the eye through this transparent
  surface
• The cornea protects the eye
• It also acts as a lens bending light waves as
  they enter the eye

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Iris

• Is a ring of muscle that contracts and expands
• This changes the amount of light that enter the
  eye
• Also give the eye color

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Pupil

• Looks black
• As light dims, the pupil enlarges allowing in
  more light
• Vis versa

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Lens

• Behind the pupil
• Refracts light, forming and image
• Page 257

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Retina

• Layer of cells lining the inside of the eye
• Contains many of tiny, light-sensitive cells
  called, rods and cones

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Rods

• Rods contain pigments that react to small amounts
  of light
• Important for seeing at night

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Cones

• Respond to color
• Three types red, blue, and green
• Function with bright

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Optic Nerve

• The signals generated by the rods and cones
  travel to the brain along a short, thick nerve
• The brain turns the image right-side up

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Correcting Vision

• Lenses in glasses are either concave or convex
• The type of lens used depends on whether the eye
  is too long or too short

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Nearsightedness

• Person can see nearby things clearly, but objects
  at a distance appear blurry
• Eyeball is a little to long
• Concave lens correct this

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Farsightedness

• Person can see far away, but objects nearby
  appear blurry
• Eyeball is too short
• This is corrected with convex lenses

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