Topic 4.2 Pages 288 - 292 1.Reflection, Absorption, and Transmission of Light by Objects 2....

Topic 4.2Pages 288 - 292

1. Reflection, Absorption, and Transmission of Light by Objects

2. Reflection and Absorption of Colours

Copyright © 2010 McGraw-Hill Ryerson Ltd.

(Pages 286-93)

Today we will learn ...

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.


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

• 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 DirectionReflection — 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.


Absorption – Light Is Converted to HeatAbsorption – 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.”


Reviewing Reflection and AbsorptionReviewing Reflection and Absorption

Click the “Start” button to review the reflection and absorption of light.

http://www.mytextbook.ca/product/9780070318533/itr/ppt/assets/SciLinks10.Unit04_Pg288_RayAbsorb_REV.SPL.swf.html


Transparent, Translucent, and Opaque ObjectsTransparent, Translucent, and Opaque Objects

Objects or materials are considered to be transparent, translucent, or opaque depending on how light behaves when it hits them.


Transparent materials absorb and reflect very little light. Example: a clear window.



Translucent materials allow light to pass through but scatters it in different directions.



Opaque objects absorb and reflect light, but they do not transmit it.



What examples of transparent, translucent, and opaque materials or objects can you think of?



Objects can absorb some colours and reflect or transmit others.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.

The pepper reflects only ____ light.

The apple reflects only ___light.


Objects can absorb some colours and reflect or transmit others.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 red

The pepper reflects only green

ACTIVITY 4.3: Page 292 of textbook

Exploring the Properties of LightIn 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.

Topic 4.2 Pages 288 - 292 1.Reflection, Absorption, and Transmission of Light by Objects 2....

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