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Try, Try, and Try Again LEARNING EVENT What is this learning event all about? Students conduct investigations, experiencing how scientists need to

have patience and perseverance when conducting inquiries. Students will follow instructions to investigate refraction of light energy, causing white light to bend and separate into the series of colours called the spectrum. They will note that scientists often make many different observations as they seek to understand phenomena.

What do you need to know? Perseverance and patience are important aspects of scientific inquiry

and technological design. As scientists and engineers seek solutions and understanding, they make multiple observations and tests to compare results, make connections and look for patterns. The reliability of results is an important factor in scientific investigations. Reliability can be achieved in a number of ways. Investigations are repeated with all factors and variables remaining constant, in order to determine if the same results occur. Another form of reliability is determining if the same results can be achieved through different means. Whenever light moves from one medium, like air, into something clear or transparent, like water or glass, it slows down just a little bit. As we learned in the last learning event, if it hits the water or glass at an angle other than 90 degrees, it bends as it slows down, something we call ʻrefractionʼ. How much that light bends when it hits something like water partly depends on the colour of the light. White light from the sun is really made up of all the colours of the rainbow, or spectrum. When there are many tiny water droplets in the sky, like after a rainstorm, the sunlight beaming through them refracts, slows down, and results in a rainbow. Different coloured light is traveling at slightly different speeds.

What preparation is required?

Introduction The introduction for this learning event does not require any particular materials.

In Action Each pair of students will need a copy of Task Card 4-M&E-8-1 a copy of Task Card 4-M&E-8-2 water a small piece of cotton cloth (square of cloth from an old T shirt or an old, clean handkerchief) an old CD or DVD a glass

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Learning Event #8 58

a flashlight a piece of white paper an aluminum pie plate 2 toothpicks scissors a piece of newspaper some pieces of dark construction paper (brown, blue or black) a bottle of clear nail polish (This will not be provided to each group of students, but rather you will place one drop onto each groupʼs aluminum pie plate at the appropriate time.)

a lamp with a 100W bulb (without its cover) set up in a corner of the classroom

Introducing the Learning Event

Ask the students to identify all of the different colours that peopleʼs eyes can be and record the list on the blackboard or chart paper. You may need to have the students determine how to group colours so that there are manageable number of choices, e.g., brown, blue, green, grey. Challenge the students to predict which colour is the most predominant eye colour in the class and record the number on a chart. (1st)

Predicting Eye Colour

Ask five students to tell the rest of the class what colour their eyes are. Have the students think about their original prediction. Based on this new information they can either stay with their first idea of what the most predominant eye colour is, or they can change their mind. Record the results on the chart (2nd). Ask another five students to identify their eye colour and, again, have the class vote on their prediction for the most predominant eye colour. Record their response on the chart. (3rd) Repeat this until the whole class has been asked what colour their eyes are. What do you notice about the predictions on the chart? Why are people changing their predictions? At what point did the information on the chart stop being a prediction? At what point on the chart did most peopleʼs predictions stop changing? Why? Tell the students that scientists often have to repeat an experiment over and over again to see if they keep getting the same results. Sometimes scientists try different experiments to see if they can get the same or similar results.

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Learning Event #8 59

In Action What is the teacher doing? What are the students doing?

Direct students to the two task cards and have them work to complete the tasks and answer the questions found on them.

Students will be working independently and following the written instructions on the two task cards. 4-M&E-8-1 Making a Rainbow Students are investigating light spectrums. They will find that there are optimum positions where they can hold the flashlight to produce a coloured spectrum on the paper. This will depend on the angle of the flashlight, making sure that the light is passing through both the glass and the water, slowing the light down and producing the spectrum. The second activity produces a starburst of faint yellow and orange colours. The light from the lamp is hitting the tiny cloth fibres and being dispersed or diffracted. When the students move the cloth they are holding they will find that the pattern moves with it. Like water drops in a rainbow, the surface of the CD in the third activity separates the white light into all of the colours that make it up. The CD is actually made of a thin coating of aluminum, covered by some plastic. The colours are produced when the light hits the tiny ridges on its surface. 4-M&E-8-2 Catching Rainbows Light is reflecting from the top of a very thin layer of nail polish to the bottom of the layer where the nail polish meets the dark construction paper, producing the colours that are seen. Much like the colours on a soap bubble or oil on the surface of a puddle, the white light is separated into its colours. Coloured spectrums like this are found in nature too. Hummingbirds, pigeons and many other birds have feathers on

parts of their bodies that make these shimmery colours. The bodies of some kinds of insects (like beetles) and the scales on some kinds of fish also shimmer with colour in the same way.

In all cases, white light is being refracted, causing it to bend and slow down so that the colours that make it up are seen

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Reflecting Have students reflect upon the reliability of their inferences or

conclusions. What observations did you make? What did you infer or conclude from these observations? How did the number of investigations help improve the reliability of your inferences or conclusions? What have you learned about making your inferences and conclusions more reliable? Students who worked in groups should review how well they worked with their partner(s) on the task cards. How well were you and your partner able to share the work? What helped you and your partner accomplish the activities on the task cards? How might you and your partner have worked even better on the tasks?

Assessing the Learning Following the lesson, jot note your observations of students. Here are

some areas you may wish to assess. How well are students able to: follow written directions; make and keep records of their observations; make interpretations based on their observations; interpret the results of multiple investigations and/or multiple trials to improve the reliability of their inferences or conclusions, and explain the importance of reliability in science and technology? Use Assessment Card 4-M&E-8 to engage your students in a performance task that assesses learning over learning events 5-8.

Linking the Learning Mathematics: graphing

Use the data on the eye colour of the class to demonstrate how that information can be displayed in chart form, which then can be illustrated in a graph. Have the students organize a way to survey other classes of students in the school to determine if the results from the class eye colour survey are the same with other groups of students. The students can utilize what they have learned about charts and graphs to illustrate the information from their survey.

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Learning Event #8 61

Extending the Learning

Provide students with a plastic cup three-quarters full with a mixture of water and a few drops of dish soap. Taking a straw the students can blow air into the liquid, producing bubbles that will heap above the top of the cup. Students can observe the colours that appear on the surface of the bubbles. If students add a small amount of powdered or liquid poster paint to the mixture, the bubbles will not have the same colours of the spectrum, however if a piece of white paper is gently placed on top of the heaped bubbles they can make a print of them. Have the students explore how they could improve the reliability of this activity. What factors need to be measured and kept consistent? What things could be changed with little or no effect on the results?

Eye Colours in Our Class

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Learning Event #8 62

Light and Sound Task Card 4-M&E-8-1 Making a Rainbow

1. Set a half-filled glass of water on a sheet of white paper

on your desk.

2. Do not move the glass of water. Use the flashlight to shine light on the glass from many different angles.

What do you observe? Where does the flashlight need to be for colours to be seen on the piece of paper?

3. Stand about two metres from the lamp in the corner of the

classroom (do not go any closer to the lamp).

4. Hold a piece of cotton cloth at eye level and stretch it with both hands.

5. Look at the light through the cloth.

What do you observe? Why to you think this is happening?

6. Take an old CD and carefully examine it.

What do you observe?

7. Tilt the CD back and forth.

What do you observe?

8. Shine a flashlight on the surface of the CD and hold that piece of white paper so that the light reflecting off the CD shines on the paper.

What do you observe? Why do you think this is happening?

Permission to photocopy granted to purchasing school only Ontario Association of Junior Educators - OAJE Light and Sound Task Card 4-M&E-8-2

Catching Rainbows

1. Fill the aluminum pie plate with about 2 cm of water.

2. Cut out four small squares of dark coloured construction paper (about 8 cm square).

3. Put one piece of paper into the water and press down on it until it is totally wet. What do you observe?

4. Add one drop of clear nail polish to the water in the aluminum pie plate.

5. If the piece of paper is floating, use a couple of toothpicks to push it down into the water.

6. Carefully and slowly lift the paper square out of the water and tilt it a bit so that the water runs off of it.

7. Lay it down on a newspaper to dry.

8. Do this for each of the four squares of paper.

9. When they are dry, pick one up and hold it under a bright light or out in the sunlight. • What do you observe when you hold the piece

of paper in bright light?

• Why do you think this is happening?

• What do you think is causing each paper square to be different?

• Where else have you seen colours like these ones?

• What do you think is causing those colours?

Permission to photocopy granted to purchasing school only Ontario Association of Junior Educators - OAJE

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Learning Event #8 63

Light and Sound Assessment Card 4-M&E-8 Lights on a Bicycle

Think about where lights are found on this bicycle.

• List where lights can be found on the bicycle.

• Describe how they work, why we are able to see them and when they work.

• Identify which properties of light they need to work.

• Suggest reasons why it is important to have different kinds of lights on a bicycle.

Permission to photocopy granted to purchasing school only Ontario Association of Junior Educators – OAJE

Imagine that you are going to test two different kinds of bicycle reflectors.

• Describe the experiment you would do to determine which reflector works the best.

• How would you make sure your results are reliable?

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