Unit C Lesson C2 Light Properties and Technologies

Lesson C2: Light Properties and Technologies

Key Ideas     Unit Checklist

  Video Lesson

What are the characteristics of light? What technologies use the unique characteristics of light to do useful tasks? Watch this video to discover more.

 

 

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  Lesson C2: Light Properties and Technologies

Reading and Materials for This Lesson

Science in Action 8
Materials:

Optical Data Storage

Compact discs (CDs), digital video discs (DVDs), and Blu-ray discs store digital information. This information includes music, movies, and video games.

CDs, DVDs, and Blu-ray media are plastic discs coated with a thin layer of shiny aluminum metal and an outer clear protective layer. Many tiny pits are stamped into the plastic discs. The tiny pits represent the digital data on the disc.

An optical disc player contains a laser that shines on the spinning disc. Laser light reflects off the disc’s pits. The player converts this reflected laser light pattern into digital bits and bytes for a computer processor to use. More information can be stored on a disc when the tiny bumps and pits are located very close together. However, not all lasers can read the pits once they get very small and close. Blu-ray drives use a violet laser, which has the shortest visible light wavelength, to read the smallest, highest density optical disks. This is why Blu-ray disks hold so much more information than DVD or CD disks.

 Watch More

Optical Discs and Laser Colour

Watch this video to learn about the invention of the compact disc.

 

 

 

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Watch this video to see the difference between DVD and Blu-ray drives.

 

 

 

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Watch this video to learn about Blu-ray disks, the last of the optical disks.

 

 

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  Connections 

Connections – Math
>> The Speed of Light

Sometimes science fiction movies talk about making objects travel at the speed of light. What is the speed of light?

Scientists use the symbol c to describe the speed of light. In a vacuum, where there are no other particles around for light to interact with, c equals 299 792 458 meters per second. The speed of light is sometimes rounded to 300 000 000 meters per second, for simpler calculations.

Physical objects don’t normally travel anywhere near speed of light. Scientists have figured out how to make very tiny particles travel close to the speed of light in big machines called synchrotrons. Canada has a synchrotron in Saskatoon, Saskatchewan, which produces images that help scientists learn more about particles.
If we know how far away an object is, we can use the speed of light to calculate how long it takes light to travel from the object to our eyes.

The speed of an object is calculated by dividing the distance an object travels by the time it takes to travel. We can mathematically express this relationship by:


From this relationship, we can also calculate time as:

How long does it take for light to travel from the Sun to Earth? The Sun is 150 billion meters away from Earth. We know that the speed of light is 300 000 000 meters per second. We can now calculate light’s travel time with:


It takes 500 seconds for light to travel from the Sun to Earth. Since there are 60 seconds in 1 minute, we can calculate 500 divided by 60 equals 8.3 minutes for light to travel from the Sun to Earth. If you look outside, any light reaching your eyes left the Sun 8.3 minutes ago!

Try calculating the answers to the following questions. Type or write your answers. When you have your answers, click the questions for feedback.

 Watch More

The Speed of Light

Watch this video to learn more about the speed of light.

 

 

 

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How did scientists first figure out that light had a speed? Watch this video to learn more.

 

 

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Law of Reflection

This online simulation explores how light rays reflect from surfaces. Click here to open the online reflection simulation and work through the instructions.

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Questions:

After you have finished all three investigations with the online simulation, carefully consider the following questions. Then, type or write your answers. When you have your answers, click the questions for feedback.

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  Connections 

Connections – Technology
>> Fibre Optics

Fibre optic technology allows us to send information at high speed around the world. The speed of light provides fast internet and telephone connections through fibre optic cables.

Fibre optic cables are long bundles of optical fibres. Optical fibres are thin, flexible glass tubes. Light reflects down the length of these tiny glass tubes, sending digital information. Many light rays can reflect through a single optical fibre at the same time, making it possible to send many signals through one fibre optic cable.

Sound and digital information is changed into a light pattern by a transmitter, before the information travels down a fibre optic cable. Receivers at the other end change the light back into its original signal.

Fibre optic cables have many advantages over wire telecommunication cables. Optical fibres cost less money, transmit messages faster, send a clearer signal, and use less energy than metal wire cables.

 Watch More

Information at the Speed of Light

Watch this demonstration of light travelling through a fibre optic cable.

 

 

 

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This video explains the basics of how fibre optics work.

 

 

 

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When you visit a website from another country, information on the website travels through fibre optic cables to your internet connection. Watch this video to see how a network of undersea fibre optic cables connects the entire world.

 

 

  Try It! 

  Safety Warning

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Instructions:

1. Open the packages of lemon jelly powder and unflavoured gelatin. Pour the powders into a large bowl and mix with a spoon.
   
   
2. Boil water in an electric kettle. Pour 2 cups of boiling water into the measuring cup. Add boiling water to the jelly powder mixture, and mix until all the powder dissolves.
   
   
3. Pour the liquid jelly mixture into the 9 x 13 inch baking pan.
   
   
4. Put the baking pan with jelly into the fridge for 3 to 4 hours, until it solidifies.
   
   
5. Take the jelly pan out of the fridge. Carefully cut a 1 inch side by 13 inch long strip of jelly and lift it out of the pan onto the plate. Use both hands to lift the jelly so that it does not break.
   
   
6. Take the jelly strip plate and a laser pointer into a dark room.
   
   
7. Aim the laser pointer at the floor and turn it on. Aim the laser pointer at a 45 degree angle into one end of the jelly strip. What do you observe?
   
   
8. Watch this video to see a version of this experiment and its results:
   

 

 

Questions: 

Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.

Lasers

The word laser stands for “Light Amplification by Stimulated Emission of Radiation”. Lasers emit a focused, high-energy beam of a single colour of light. Lasers were invented in 1960, and have been used for many purposes since then.

Click here to Explore with Elsie about the many uses of lasers. 

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  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 2 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.

1. DOWNLOAD the self-check quiz by clicking here.
   
   
2. 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.
   


3. 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.
   


4. 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.
   
   
5. 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.
   


6. 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!

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Self-Check Quiz Answers

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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.

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