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# Physics Light and Colour: A reflection - Stile handouts/Lesson 007.pdf · PDF filePhysics...

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• Physics

Light and Colour: A reflection

This lesson sheds light on why the sky is blue. In it, you will explore the following:

What is light?

What is colour?

Wave period and frequency

Refraction and reflection

Put your sunnies and your thinking hat on and take a stroll through this lesson!

This is a print version of an interactive online lesson. To sign up for the real thing or for curriculum details about the lesson go to www.cosmosforschools.com

• Introduction: Light and Colour (P1)

Why is the sky blue? This question puzzled people for thousands of years. It wasnt simple to answer, either. And even now youmay wonder why it isnt dark like space or bright yellow like the Sun.

To answer the question, scientists first had to work out what made colours. That led them to think about what light was and how itworked. Only then could they start to think about how light might react to other things in the atmosphere to make the sky blue.

Although many brilliant men, starting with Isaac Newton, the cleverest scientist of the 17th century, tackled the problem, no oneperson could answer it without the work of others. It took hundreds of years to put the pieces together, with each generationfollowing Newton working out a new piece.

The whole history is like a long detective story.

Read the full Cosmos Magazine article here

Sir Isaac Newton discovered that light could be split into the colours of the rainbow using a glass prism. Source: iStock

• Question 1

Think: If you could travel back in time and speak with Sir Isaac Newton, what would you ask him? Why?

• Gather: Light and Colour (P1)

From the above video, we have just learned that waves have a period and a frequency. A period is how long it takes for a wave to gothrough its full motion once and a wave's frequency is how many waves go by in a second.

Question 1

Calculate: You throw a large rock into a pond and notice that as the ripples start to reach the shoreline that three waves break onthe shore for every second that goes by. What is the period of the wave created by the splash?

Question 2

You may optionally upload a photo of your working out for question 1 below.

Drag and drop file here

• Question 3

Recall: Why can't we see light as a wave in the same way that we can see ripples in a pond?

Question 4

Recall: What is the visible spectrum of light?

The science behind single and double rainbows.

Question 5

Apply: In the above video, meteorologist Aaron Pickering mentions that light bends when it enters a rain drop. Another word usedto describe light bending is refraction. He goes on to say that light reflects off the back of the rain drop. Most objects reflect light,which is what enables us to see them

In the table below list three objects that you can think of that refract light and objects things that reflect light.

Objects that refract light Objects that reflect light

1 e.g. glasses e.g. mug

2

3

4

• Process: Light and Colour (P1)

Source: iStock.

Question 1

Explain: Why do leaves appear green?

Question 2

Infer: What colour do you think the above leaves would appear if you shone a pure red light on them at night time? Why?

Question 3

Explain: Why does dark blue bitumen become unbearably hot to touch after a hot and sunny summer's day yet pale grey concretedoes not?

• Question 4

Create: You have been commissioned by Cosmos Magazine to design an item of clothing of your choice. The item has to besuitable for both summer and winter.

Describe and illustrate your item of clothing in the project space below. Be creative and make sure you justify each of your designchoices including your choice of shape, material and colour.

If your teacher is agreeable, you may work in pairs.

• Apply: Light and Colour (P2)

Experiment: Making big bubbles

To examine the properties of bubbles (and to have some fun).

1250 mL soft drink bottle

200 mL concentrated pure soap liquid.

50 mL glycerine

1 L water

2 straws

String

Plastic tray or container

Camera (optional)

Part 1 - Making your bubble mixture

To make your bubble mixture simply mix the water, soap liquid and glycerine in the soft drink bottle. Shake the mixture well and letit sit until it settles (for the best mixture let the mixture sit for 24 hours).

Part 2 - Making your bubble wand

You will need to make a bubble wand. Cut a piece of string to about 1.5 meters in length. Thread the string through both strawsand tie it off.

Aim

Materials

Method

• Go outside and find an open space with little to no wind. Pour your bubble mixture into your plastic tray or container. Dip yourbubble wand into your bubble mixture, hold it up so that the breeze is at your back and watch the bubble form before your eyes.

Try to make a bubble as big as possible.

Try to make a bubble last as long as possible.

Observe

Question 1

Answer the observation questions in the table below.

What colours did you see in your bubbles?

Where is the bubble thickest?

What did you do to make your bubble as big aspossible?

What did you do to make your bubble last aslong as possible?

Question 2

Drag and drop file here

Discussion

Question 3

Describe how light interacts with the bubbles.

Question 4

Part 3 - Make your bubbles

• Question 5

Explain your answer to what did you do to make your bubble last as long as possible?

• Career: Light and Colour (P2)

Threading a needle can be difficult and using tweezers to remove a splinter perhaps harder still. But imagine that your job isto manipulate matter at the atomic scale. Impossible? Not for Bent Weber, a physicist at the University of New South Wales' Centrefor Quantum Computation and Communication Technology, in Sydney.

Bent grew up in Germany and initially wanted to be a journalist.He studied a range of subjects in his final years of schoolincluding arts, sports and languages, but it was his impressivehigh school physics scores and that led, instead, to a physicsdegree at the University of Hamburg.

Bent works with special electronic devices to create wire justfour atoms wide and one atom high. "We test how small we canmake electrical components," explains Weber. "We've shown wecan essentially make them as small as a couple of atomswithout a loss of functionality - they behave just as if they were amuch larger structure."

Modern computers, mobile phones and other digital devicesfeature miniaturised electronic circuits on silicon chips, withinterconnecting wires. Future devices such as quantumcomputers may solve larger and more complicated problems atspeeds that beat even the fastest of todays computers. But theywill require nanoscale wires and that's where Weber's researchcomes in. Bent's group has created the narrowest conductingsilicon wires ever.

Bent enjoys the flexibility that his line of work can offer. Somedays he has to conduct gruelling overnight experiments, but ifhe does then he can turn up to work a little later than usual thefollowing morning. The main thing is that he has to get the jobdone, and he does. Bent is highly stimulated by the challengesof his work and is excited to be on the forefront of "pushing thebounds of human knowledge and what is technologicallyachievable."

Bent currently lives in Sydney and thrives on the contrast in hislife between the unpredictable thrills he gets as a surfer, ridingwaves on Sydney's beaches, and as a physicist, requiring wellthought-out calculated moves in the laboratory.

Bent Weber at work

• Question 1

Imagine: Bent enjoys the contrast of working hard in the lab as a physicist during the week and surfing on the weekends. Below,write down your ideal combination of job and hobby. What is it about this combination that appeals to you?

Cosmos Lessons team

Education Editor: Bill CondieArt director: Robyn AdderlyLesson authors: Daniel Pikler and Sally Parker

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