LIGHT - Classification of materials:
OUTCOMES:
Students classify materials as transparent, opaque or translucent, based on whether light passes through them (is transmitted), is absorbed, reflected or scattered
NOTE: Absorption is covered in more detail in the next section.
Students learn:
| Curriculum | Learning Activities |
|---|---|
| SCIENCE | Identify scientific principles underlying bhaviour of light |
| TECHNOLOGY | Record and analyse data |
| ART | Blended multimedia elements |
| ENGINEERING | Design, build and test experimental device(s) |
| MATHEMATICS | Use comparative data to differentiate materials |
MATERIALS:
Example materials list - More (optional) infrared detail is available: here
- One or more (shared) infrared camera(s), set up on IWB using Videolan (VLC) software free download and pre-loaded on DoE esktop computers.
- A sheet of white paper approximately 75mm square (to fit unfolded into a standard sized envelope
- Three marker pens - black, red, blue or green (or similar colours).
- A minimum of one small torch (visible light source) for each group
- One or more TV remote control (or similar infrared controller(s) as infrared light source)
- A range of materials including, vinyl, paper (including white, coloured, patterned), cloth (including white, coloured, patterned)
- Google sheet or science journal to record results
- Make a guess (your 'hypothesis') about which materials you think are transparent, opaque, or translucent (write down what you think you will see)?
PROCEDURE:
- Make three large marks on the white paper using only one colour for each mark - using black, blue and green markers. This will be called our 'test message'
- Place the test message on a flat surface and place each of the test materials over the message.
- Try shining the torch through the material and see if the message is visible through the material - both with torch on and with torch off.
- Record the results of message visibility when covered by each material. The results can be recorded in science journal/spreadsheet, and an (optional) digital photograph for each test.
OBSERVATIONS:
- First try the card with the smaller hole and write down what you see.
Results Table #1 - Test materials using visible light (eyes/camera) & test message
Place your 'test message under each of the following materials, record if you think the materials are transparent or absorb, reflect and/or scatter visible light:
| Material | Some Transparent | Some Absorbed | Some Reflected | Some Scattered |
|---|---|---|---|---|
| Clear bottle full water | yes | no | yes | no |
| Blue Wooden ruler | no | no | Yes | no |
| Clear empty plastic bottle | yes | no | no | yes |
| Red postal envelope | no | yes | no | yes |
| Black vinyl | no | yes | no | yes |
| Gift wrapping paper | no | yes | yes | yes |
| .. and so on… |
PROCEDURE 2:
- Repeat the experiment by inviting each group to choose one opaque material and repeating the experiment - place the message under the opaque material and try to read the message using the Infrared camera
- Try placing the infrared controller below each material and clicking a control.
- Can you see the light through the material using your eyes only
- Does the infrared camera show the light from the controller passing through the material?
- Each student should record the results in their science journal/spreadsheet. The infrared camera can optionally be used to take a snapshot of each example?
Results Table #2 - Testing materials using infrared camera & test message
Place your 'test message under each of the following materials, record if you think the materials are transparent or absorb, reflect and/or scatter visible light:
| Material | Some Transparent | Some Absorbed | Some Reflected | Some Scattered |
|---|---|---|---|---|
| Clear bottle full water | yes | no | yes | no |
| Blue Wooden ruler | no | no | Yes | no |
| Clear empty plastic bottle | yes | no | no | yes |
| Red postal envelope | no | yes | no | yes |
| Black vinyl | no | yes | no | yes |
| Gift wrapping paper | no | yes | yes | yes |
| .. and so on… |
RESULTS:
Choose one example where the results for the visible light using your eyes or ordinary camera are different to the results seen when using the infrared camera.
Draw and label two ray diagrams - Draw one ray diagram for the visible light and one other diagram for the infrared light.
Q 1. Do clear/transparent materials absorb or reflect any light?
- Write down what you think
Q 2. Did light from the infrared controller shine through any of the materials when viewed through the infrared camera?
Q 3. Can you explain why the infrared light did, or did not shine through the material?
- Write down what you think
DISCUSSION:
In the old days, people believed in the existence of three separate types of radiation:
- Light
- Heat radiation
- Actinic radiation.
Eventually scientists discovered that all three were actually the same stuff: light. “Heat radiation” and “actinic radiation” are simply invisible light of various frequencies. Today we say 'Infrared light' rather than 'Heat radiation' and 'Ultraviolet or UV light' rather than 'Actinic radiation'. 1)
Is there any difference between what you see on the wall when you compare when light shines through the small hole compared with when light shines through the larger hole (write down what you think)?
- Light waves and colour
- Reflection and the ray model of light Reflection interactive
- Refraction and the ray model of light Refraction interactive
Video 3. Refraction & Colours Explained
- IF UNABLE TO ACCESS YOUTUBE VIDEO (requires Flash) TRY: Viewpure Refraction & Colours Explained
CLASSROOM ACTIVITY: Complete a 'marching soldier analogy' experiment