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.
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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.
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3. Shadows A shadow is created when an opaque object absorbs light rays.
Shadows demonstrate that light travels in straight lines.
A ray diagram shows how the distance from the light source affects the size of the shadow an object makes.
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4. Reflection is when light bounces off of an object.
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
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5. The normal is an imaginary line perpendicular to the surface.
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.
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6. This change in speed causes the light to change direction.
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.
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7. 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.
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Take the Section 5.1 Quiz
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