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 wasn’t simple to answer, either. And even now you
may wonder why it isn’t 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 it
worked. 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 one
person could answer it without the work of others. It took hundreds of years to put the pieces together, with each generation
following Newton working out a new piece.
The whole history is like a long detective story.
Read the full Cosmos Magazine article h
​ ere
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)
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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 go
through 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 on
the 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?
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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 used
to 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
1
2
3
4
e.g. glasses
Objects that reflect light
e.g. mug
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 concrete
does not?
Question 4
Create: You have been commissioned by Cosmos Magazine to design an item of clothing of your choice. The item has to be
suitable 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 design
choices 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
Aim
To examine the properties of bubbles (and to have some fun).
Materials
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)
Method
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 let
it 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 straws
and tie it off.
Part 3 - Make your bubbles
Go outside and find an open space with little to no wind. Pour your bubble mixture into your plastic tray or container. Dip your
bubble 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.
Optional: take photos of your bubbles and upload your favourite photo to your teacher.
Observe
Question 1
Answer the observation questions in the table below.
Question
What colours did you see in your bubbles?
Where is the bubble thickest?
What did you do to make your bubble as big as
possible?
What did you do to make your bubble last as
long as possible?
Question 2
Upload your favourite bubble photo here.
Drag and drop file here
Discussion
Question 3
Describe how light interacts with the bubbles.
Question 4
Explain your answer to ​where is the bubble thickest?
Answer
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 is
to manipulate matter at the atomic scale. Impossible? Not for Bent Weber, a physicist at the University of New South Wales' Centre
for 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 school
including arts, sports and languages, but it was his impressive
high school physics scores and that led, instead, to a physics
degree at the University of Hamburg.
Bent works with special electronic devices to create wire just
four atoms wide and one atom high. "We test how small we can
make electrical components," explains Weber. "We've shown we
can essentially make them as small as a couple of atoms
without a loss of functionality - they behave just as if they were a
much larger structure."
Modern computers, mobile phones and other digital devices
feature miniaturised electronic circuits on silicon chips, with
interconnecting wires. Future devices such as quantum
computers may solve larger and more complicated problems at
speeds that beat even the fastest of today’s computers. But they
will require nanoscale wires and that's where Weber's research
comes in. Bent's group has created the narrowest conducting
silicon wires ever.
Bent enjoys the flexibility that his line of work can offer. Some
days he has to conduct gruelling overnight experiments, but if
he does then he can turn up to work a little later than usual the
following morning. The main thing is that he has to get the job
done, and he does. Bent is highly stimulated by the challenges
of his work and is excited to be on the forefront of "pushing the
bounds of human knowledge and what is technologically
achievable."
Bent currently lives in Sydney and thrives on the contrast in his
life between the unpredictable thrills he gets as a surfer, riding
waves on Sydney's beaches, and as a physicist, requiring well
thought-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 Condie
Art director: Robyn Adderly
Lesson authors: Daniel Pikler and Sally Parker