Ray Optics: Reflection and Refraction

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Ray Optics Reflection and Refraction

• 10.1

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Rays

• Representation of the path that light follows
• Represent beams of light that are composed of
  millions of light photons traveling together

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Reflection

• When a light ray strikes the surface of a
  material and some of the light bounces off the
  surface

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Reflection

• Normal line
• Perpendicular to the surface at the point of
  reflection
• Angle of incidence
• The angle between the incoming light ray and the
  normal line
• Angle of reflection
• The angle between the normal line and the
  reflected ray.

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Reflection

• The angle of incidence is always equal to the
  angle of reflection

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Reflection

• Flat mirrors
• Plane mirrors
• Produces an image that is reversed and appears to
  be located the same distance behind the mirror as
  the object is in front of the mirror

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Reflection

• Spherical mirrors
• Convex
• Outside surface (back) of a spoon
• Concave
• Inside surface (front) of a spoon

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Reflection

• Focal Point of a Flat Mirror
• The point in front of the mirror at which the
  reflected rays all meet
• Spherical mirrors or lenses do not have exact
  focal points.
• Focal point of a concave mirror is in front of
  the mirror
• Focal point of a convex mirror is behind the
  mirror

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Reflection

• Real image
• Formed by a mirror or lens when light rays from
  the object converge. It can be seen by placing a
  screen or piece of paper at the point at which
  the light from the object converges.
• Virtual image
• Apparently causes light to diverge from a mirror
  or lens. It cannot be seen on a screen or piece
  of paper since no light actually converges at the
  image location.

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Refraction

• The change in direction of a wave or photon of
  light as it crosses a boundary into a different
  medium
• Index of refraction is the ratio of the speed of
  light in a vacuum to the speed of light in the
  material

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Total Internal Reflection

• When the angle of refraction is greater than 90º,
  a light ray is reflected.
• Optical fibers
• Light stays in the fiber because each interaction
  of the light bouncing off the side is reflected

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Lenses

• A carefully ground or molded piece of transparent
  material
• Convex lensthicker at its center than at its
  edges (converging)
• Concave lensthinner at its center than at its
  edges (diverging)