The Ray Model of Light and

• • Transparent: lets almost all light pass through
• • Translucent: some light can pass through
• • Opaque: no light can pass through
• • Mirror: any polished surface that reflects and image
• • Image: reproduction of an object using light
• • Reflection: when light bounces back of a surface
• • Plane mirror: a flat mirror
• The Ray Model of Light

  • A light ray is a straight arrow representing direction/path of light
  • Geometric optics use light rays to determine the path of light when it strikes an object
• Shadows

  • Ray model of light can be used to  understand how shadows form and how light is reflected 
  • A shadow is a dark region that forms behind an object that is being illuminated more brightly on one side than the other
  • A shadow from when an opaque object blue the direct light from a source

  1. The umbra - the darkest part of shadow
  2. The penumbra - lighter part of shadow
• Incident: light ray emitted from a source that strikes an object
• Reflected ray:  light ray that bounces off the mirror or reflective surface
• Angle of incidence: the angle between the incident ray and the normal
• Laws of Reflection

  • The angle of incidence equals the angle of reflection
  • The incident ray, the reflected ray, and the normal all lie in the same plane
• Specular Reflection

  • Reflection of light off a smooth surface
  • Occurs when: flat surface reflects all incoming parallel incident rays at the same angle
  • EG: reflection off a plane mirror, reflection off still water
• Diffuse Reflection

  • Reflection of light off an irregular, dull, or rough surface
  • Occurs when: rough surface reflects all incoming parallel incident rays not the same angle bc the angle of surface changes the angle of incidence for each incoming ray
  • Incident rays are parallel and reflected rays are not