The Plan…
19 April 2013
• Any concerns with Chapter 4 Test?
 Test Assessment & re-test sign up
• Start Chapter 5
• 5.1 – Ray Model of Light
 PowerPoint & Worksheet
 Worksheet is Homework
• Reading Checks
 P. 171 & 175
• Title Page due WEDNESDAY
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(c) McGraw Hill Ryerson 2007
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.
See page 168
(c) McGraw Hill Ryerson 2007
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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
(c) McGraw Hill Ryerson 2007
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Transparent, Translucent, & Opague
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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.
See page 171
(c) McGraw Hill Ryerson 2007
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Light Can Be Reflected
• Reflection is when light
bounces off of an object.
Incident ray
Reflected ray
 To act like a mirror, the surface
must be smooth.
 A Rough surface reflects light
randomly
• The incoming ray of light is
called the incident ray.
• The ray that bounces
off the surface is called
the reflected ray.
See page 172
(c) McGraw Hill Ryerson 2007
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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. (This is the i in the diagram)
• The angle of reflection is measured from the normal to the
reflected ray. (This is the r in the diagram)
The angle of incidence equals the angle of reflection.
See page 173
(c) McGraw Hill Ryerson 2007
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Light Can Be Refracted
• When light travels from one
transparent medium to a
transparent medium it changes
speed. I.e. from air to water…
 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
(c) McGraw Hill Ryerson 2007
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Rules of Refraction
• When light hits water it either slows down or speeds up:
 When light travels from air to water, the light “Slows down and bends
towards normal.”
 When light travels from water to air, the light “Speeds up and bends
away from normal.”
(c) McGraw Hill Ryerson 2007
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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
Take the Section 5.1 Quiz
(c) McGraw Hill Ryerson 2007
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Your turn…
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5.1 Worksheet (Due Monday)
Vocab
Title Page (Due Wednesday)
Monday – Activity 5.2
You have 1 week to hand in missing work from Ch 4
Sign up for re-test
 Tues-Weds-Thurs next week
• Your marks are up to date
 These are your report card marks, missing something DO IT!
• Questions?
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(c) McGraw Hill Ryerson 2007