Transcript 05-SNC2P_(4.2)_Reflection_AbsorptionOfColour_ Transmission

1. Reflection, Absorption, and
Transmission of Light by
Objects
2. Reflection and Absorption of
Colours
Topic 4.2
Pages 288 - 292
Today we will learn ...
(Pages 286-93)
1. Light can be reflected, absorbed, or
transmitted by objects.
2. Objects can absorb some colours and
reflect or transmit others.
3. Light travels in a straight line.
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A ray is an arrow that shows the direction in which light is
travelling.
Scientists use diagrams called ray diagrams to help them
understand and make predictions about how light behaves.
RAYS
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• Transmission: Light passes
through an object and continues
travelling. Example: Clear glass.
• Absorption: Light is absorbed by
(remains in) the object and
turned into heat.
• Reflection: Light bounces off the
object and travels in another
direction.
Reflection — Light Changes Direction
In A the person sees the object because light travels
to their eyes. B shows that light must travel from a
source (the lamp) and then reflect off the object
toward the eye.
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Absorption – Light Is Converted to Heat
The “E” in the image above appears black because
the ink absorbs all of the light that hits it. No
light reaches your eyes from the printed “E.”
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Reviewing Reflection and Absorption
Click the “Start” button to review the reflection and absorption of light.
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Transparent, Translucent, and Opaque Objects
Objects or materials are considered to be transparent,
translucent, or opaque depending on how light behaves when
it hits them.
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Transparent, Translucent, and Opaque Objects
Transparent materials absorb and reflect very little light.
Example: a clear window.
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Transparent, Translucent, and Opaque Objects
Translucent materials allow light to pass through but
scatters it in different directions.
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Transparent, Translucent, and Opaque Objects
Opaque objects absorb and reflect light, but they do
not transmit it.
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Transparent, Translucent, and Opaque Objects
What examples of transparent, translucent, and opaque
materials or objects can you think of?
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Objects can absorb some colours
and reflect or transmit others.
Opaque objects either absorb or reflect light.
The colour an object is determined by the colours (or
wavelengths) of light that are reflected by its surface and
the colours that are absorbed by the object.
Under white light, the tomato
appears to be red because only
the red wavelength is reflected.
Under blue light, the tomato
appears to be blue.
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Objects can absorb some colours
and reflect or transmit others.
The colour of an object is determined by which colours (or
wavelengths) of light are reflected by its surface and which
colours are absorbed by the object.
The apple reflects only ___light.
red
The pepper reflects only ____
green light.
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ACTIVITY 4.3:
Page 292 of textbook
Exploring the Properties of Light
In groups of 3. Amongst your group
members, decide who will be the
MATERIAL manager, the TASK manager,
and the SAFETY officer.
Every person must have a role.
• Material manager: responsible for
getting all the material and for cleaning
up.
• Task manager: responsible for
becoming familiar with the procedure,
and knowing what the group members
have to do (step by step).
• Safety officer and recorder: responsible
for any safety issues, and for submitting
the answer to question 1 for their group.
Resources:
• Cardboard tubing (4 – 8 cm in
diameter, and about 25 cm long)
• Translucent wax paper
• Aluminum foil
• Masking tape
• Push pin
All students must answer the
observation question, and contribute
to the final question which involves
drawing the ray diagram to explain
how light travels in a straight line.
On your question sheet, please write
down the names of your group
members with their responsibilities.