Topic 4.2 Pages Reflection, Absorption, and Transmission of Light by Objects 2. Reflection and Absorption of Colours

Copyright © 2010 McGraw-Hill Ryerson Ltd. (Pages ) 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.

Copyright © 2010 McGraw-Hill Ryerson Ltd. 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.

Copyright © 2010 McGraw-Hill Ryerson Ltd. 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.

Copyright © 2010 McGraw-Hill Ryerson Ltd. 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.”

Copyright © 2010 McGraw-Hill Ryerson Ltd. Reviewing Reflection and Absorption Click the “Start” button to review the reflection and absorption of light.

Copyright © 2010 McGraw-Hill Ryerson Ltd. 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.

Copyright © 2010 McGraw-Hill Ryerson Ltd. Transparent materials absorb and reflect very little light. Example: a clear window. Transparent, Translucent, and Opaque Objects

Copyright © 2010 McGraw-Hill Ryerson Ltd. Translucent materials allow light to pass through but scatters it in different directions. Transparent, Translucent, and Opaque Objects

Copyright © 2010 McGraw-Hill Ryerson Ltd. Opaque objects absorb and reflect light, but they do not transmit it. Transparent, Translucent, and Opaque Objects

Copyright © 2010 McGraw-Hill Ryerson Ltd. What examples of transparent, translucent, and opaque materials or objects can you think of? Transparent, Translucent, and Opaque Objects

Copyright © 2010 McGraw-Hill Ryerson Ltd. 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. Copyright © 2010 McGraw-Hill Ryerson Ltd. 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 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.