What is Refraction?

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What is Refraction?

• Light waves travel in straight lines through a
  medium or a vacuum
• Suppose a light wave moved from one medium to
  another, from air to water
• The wave enters the water at an angle, and the
  wave bends
• This bending of a wave as it moves from one
  medium to another is called refraction

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• In a vacuum, light travels at 300,000 km/s
• But it travels more slowly through matter
• Waves bend as they go from one medium to another
  because they change speed
• Water more dense than air
• So when a light wave moves from air into water,
  it slows down
• When a light wave moves from water into air, it
  speeds up
• Waves slow down as they move through more dense
  materials
• This change in speed causes the wave to be
  refracted, or bent

• This pencil appears broken because light bends or
  refracts when it moves from air to water

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Laws of Refraction

• All angles are measured from a line called the
  normal, which is a line at a right angle to a
  barrier.
• When a wave moves at an angle from a less dense
  medium to a more dense medium, it is bent toward
  the normal
• When a wave moves at an angle from a more dense
  medium to a less dense medium, it is bent away
  from the normal
• When a wave moves from one medium to another
  along the normal, it is not bent

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Refraction and Lenses
Concave Lens

• A lens is a transparent (see-through) material
  that refracts light.
• Lenses have either one or two curved surfaces,
  and are called concave or convex
• Eyeglasses are made with one or more of these
  lenses in order to help people see
• These lenses work by making objects appear
  smaller or larger when light is refracted through
  them
• Lenses are used to form images.
• An image is a copy of an object formed by
  reflected or refracted rays of light

Convex Lens
Focal length is the distance between the lens and
the focal point.
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• Convex Lenses
• A convex lens forms an image that depends on the
  distance from the object to the lens.
• These lenses curve outward and are thick in the
  middle
• When light rays pass through a convex lens, the
  rays are refracted toward each other

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Convex Lenses
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Concave Lenses

• Concave lenses work to make an image appear
  smaller
• These lenses bend inward, and are thin in the
  middle
• Light that passes through is bent away from the
  lens
• These lenses are sometimes combined with other
  lenses in eyeglasses, telescopes, microscopes and
  binoculars

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Where do we find lenses?

• Magnifying lenses, cameras, telescopes and
  microscopes have one or more convex lenses
• Eyeglasses are made with a combination of convex
  and/or concave lenses
• The eye is naturally shaped like a convex lens as
  a means to make objects appear larger

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• http//www.brainpop.com/science/energy/refractiona
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