5.1 The Ray Model of Light

1
5.1 The Ray Model of Light

• Some properties of light are best described by
  considering light as a wave. Other properties of
  light are best described by considering light as
  a particle.
• The ray model of light uses a straight line, or
  ray, to show the direction the light wave is
  traveling.

2
Light and Matter

• Different materials can either transmit, absorb,
  or reflect light.
• Transparent materials allows light to pass
  through freely.
• Translucent materials lets most light through but
  scatters the light leaving.
• Opaque materials prevent light from passing
  through.

See pages 169 - 170
3
Light and Matter
4
Transparent
5
Translucent
6
Opaque
7
Shadows

• A shadow is created when an opaque object absorbs
  light rays.
• Shadows demonstrate that light travels in
  straight lines.

See page 171
8
Shadows

• A ray diagram shows how the distance from the
  light source affects the size of the shadow an
  object makes.

9
Light Can Be Reflected

• Reflection is when light bounces off of an
  object.
• To act like a mirror, the surface must be smooth.
• The incoming ray of light is called the incident
  ray.
• The ray that bounces off the surface is called
  the reflected ray.

Reflected ray
Incident ray
See page 172
10
Light Can Be Reflected
11
The Law of Reflection

• The normal is an imaginary line perpendicular to
  the surface.
• The angle of incidence is measured from the
  normal to the incident ray.
• The angle of reflection is measured from the
  normal to the reflected ray.
• The angle of incidence equals the angle of
  reflection.

See page 173
12
Light Can Be Refracted

• When light travels from one transparent medium to
  a transparent medium it changes speed.
• This change in speed causes the light to change
  direction.
• The bending of light, due to a change in speed,
  is called refraction.
• The angle of refraction is measured from the
  refracted ray to the normal.

See page 174
13
Refraction of Light in Water and Air

• Objects in water appear in a different location
  than they actually are. This is due to the
  refraction of the light.
• Light refracts when it passes through air at
  different temperatures.
• For example, a mirage is the light from the sky
  bending as it approaches the warm air near the
  ground.

See page 175
14
Refraction of Light in Water
See page 175
15
Refraction of Light in Air
Take the Section 5.1 Quiz
See page 175