Humans have been curious about light for thousands of years. Our understanding of light and vision has changed over time. Watch this video to learn more about how we have increased our understanding of light.
Lesson C1: Solving the Riddle of Light and Vision
Figure C.1.1.1 – Light has characteristics of wave energy.
Figure C.1.1.2 – Light’s ability to behave as a particle makes solar panel technology possible.

Light is a Wave... and a Particle!
Light behaves as both a wave and a particle. The famous scientist Albert Einstein was the first person to imagine this in 1905.
We know light has wave-like properties because of a famous experiment that proved interacting light beams can create interference patterns (see Fig.C.1.1.4). Imagine, two sources of light creating an area of darkness! Other waves that transmit energy,
such as water and sound, also show interference patterns, so these patterns are proof that light travels as a wave.
Reading and Materials for This Lesson
Science in Action 8
Reading: Pages 176–181
Materials:
Two empty toilet paper rolls, cardboard, aluminum foil, ruler, scissors, glue, tape, pencil, clear plastic wrap, shiny coloured beads or sequins.
Light is quite special though. Even though it has wave properties, it acts like a particle too. Light particles are called photons. Solar panel and light emitting diode (LED) technologies depend on photons. Photons bump into particles in solar cells,
making charged particles move, which produces an electric current. In LED lights, electric energy makes loose charged particles move to a different position. In this process, energy is released as photons which we see as light.
Figure C.1.1.3 – In 2015, researchers recorded the first ever image of light behaving as both a wave and a particle. Image by Fabrizio Carbone.
Figure C.1.1.4 – Light waves can interfere with each other.
Watch More
The Dual Nature of Light
This video explains more about the characteristics of light as both a wave and a particle.
Light can create interesting reflection patterns. The kaleidoscope is a toy that takes advantage of this property of light.
The inside of a kaleidoscope tube is covered in mirrors. Colourful and shiny beads or glass pieces are contained at one end of the tube. When you look through the other end of the tube, the inner mirrors reflect light from the colourful beads. Light
keeps reflecting off the mirrors inside the tube, creating repeating patterns called fractals.
A fractal is a geometric pattern that keeps repeating over and over again. We often see fractals in nature, such as in tree branches or in the arms of a snowflake.
Watch More
Kaleidoscopes
Watch this video to see a turning kaleidoscope in action.
Try It!
Make a Kaleidoscope
Try this simple activity to make your own reflecting kaleidoscope.
Materials:
2 empty toilet paper rolls
Cardboard
Aluminum foil
Ruler
Scissors
Glue
Tape
Pencil
Clear plastic wrap
Shiny coloured beads or sequins
Safety Warning
Take care with scissors; don't cut yourself or anyone else!
Instructions:
Cut three rectangles of cardboard and three pieces of foil. The dimensions of each rectangle should be 3.5 cm wide by 9 cm long.
Glue one foil rectangle to one cardboard rectangle, with the shiniest side of the foil facing outward. Repeat for the other two rectangles of foil and cardboard.
Tape the three foil and cardboard rectangles along their length to form a triangular prism. The foil side of the rectangles should face inward.
Cover one end of one toilet paper roll with clear plastic wrap. Tape the plastic wrap in place to the toilet paper roll.
Cut a 1 cm wide round section off the other toilet paper roll. Tape it to the plastic wrapped end of the first toilet paper roll, extending the cylinder.
Fill this small toilet paper roll section with coloured beads or sequins.
Cover the small toilet paper roll section with a second piece of plastic wrap. Tape the plastic wrap in place to the toilet paper rolls.
On cardboard, trace around the other circular end of the toilet paper roll to make a circle. Cut out the circle. Using a pencil, punch a smaller hole in the middle of the cardboard circle.
Slide the triangular prism inside the toilet paper roll.
Place the cardboard eyepiece on the open end of the toilet paper roll. Tape it in place, sealing the edges.
Hold the small hole in the kaleidoscope end up to your eye. Slowly turn the kaleidoscope in a circle. What do you observe?
Watch this video to see this experiment and its results:
Questions:
Think about the following question very carefully. Then, type or write your answer. When you have your answer, click the question for feedback.
Light reflects off the shiny beads into the three mirrors. Light also reflects off a mirror into the other nearby mirrors. This creates multiple reflections of the same object.
Sharing:
Congratulations on completing this activity! Consider sharing your completed kaleidoscope in the course Sharing Forum. Take a photo of it and post it, your teacher
and other students would be interested in seeing how your kaleidoscope turned out!
Connections
Figure C.1.1.8 – Incandescent bulb filaments change electric energy into light energy.
Figure C.1.1.9 – Compact fluorescent bulbs use less electricity than incandescent bulbs.
Connections – Technology >> Light Bulbs
Figure C.1.1.10 – Light emitting diode (LED) lights stay cool to the touch.
Before the invention of electric lights, if people wanted to see at night, they would burn fuel, like wax in a candle or liquid fuel in a lantern.
The incandescent light bulb was first invented in 1802, although it did not become popular until Thomas Edison made a compact light bulb in 1879. When electricity travels through the thin filament of an incandescent light bulb, it changes into heat
and light.
The invention of electric light bulbs changed society. With electric light, people are able to do tasks late into the night, especially during the winter. Electric lights make cities safer to walk around at night. However, being exposed to excess
light at night can disrupt people’s sleep patterns. Light pollution can contribute to the overgrowth of photosynthesizing organisms like algae.
The light bulb has improved in design over the years. Incandescent light bulbs produce a lot of wasted heat, which wastes electricity and makes them inefficient. Two alternative types of light bulbs are more efficient than incandescent lights. Compact
fluorescent lights (CFLs) work by putting special gases inside a coated glass tube and running electricity through the tube. The interaction of the gases and electricity create ultraviolet light. The ultraviolet light makes the glass tube’s inner
coating glow. Light emitting diode (LED) lights are even more efficient than compact fluorescent bulbs. They stay cool to the touch when in operation.
Figure C.1.1.11 – Neon lights are very colourful, and are often used for advertising.
Figure C.1.1.12 – Electric lights can be seen from space.
Watch More
Light Bulbs
This video explains the difference between the three main types of household light bulbs.
Watch this video to learn more about LED lights.
Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your learning.
Unit C Lesson 1 Self-Check
Instructions
Complete the following 6 steps.
Don't skip steps – if you do them in order, you will confirm your
understanding of this lesson and create a study bank for the future.
ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.
COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.
REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct
any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.
SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.
CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum,
or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!
Be a Self-Check
Superhero!
Self-Check Quiz Answers
Click each of the suggested answers below, and carefully compare your answers to the suggested answers.
If you have not done the quiz yet – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.
Modern light bulbs waste less energy. Modern light bulbs don’t get as hot as incandescent bulbs, which means that they are more efficient. Modern light bulbs reduce our use of electrical energy, which costs less money and is better for the environment.
Reading and Materials for This Lesson
