science 8 unit c light & optical systems. unit c section 1.0 our knowledge about light and...
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Science 8 Unit C Light & Optical Systems
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Unit C Section 1.0Our knowledge about light and vision comes from explanations, inventions, and investigations.
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Section 1.0 Outcomes
• Identify challenges in explaining light and vision
• Analyze how microscopes, telescopes, and other optical devices use the properties of light
• Describe how the development of optical devices contributed to other discoveries in science
• Investigate light beams and identify phenomena that show the nature of light
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1.1 – The Challenge of Light
• People have been using optical devices for thousands of years
• Mirrors and lenses were used in ancient China and Greece
• The Greek scientist Archimedes even developed a plan to use light reflected from mirrors to burn enemy ships in Syracuse harbour!
Mythbusters – Archimedes Death Ray Fan Challenge
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Early Light Ideas
• In ancient Greece, a number of people studied light
• In the 6th century B.C., a mathematician known as Pythagoras tried to explain how light worked:
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Problems With Pythagoras’ Theory:
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Euclid & Ptolemy:
• Euclid discovered two important properties of light:
1.
2.
• Ptolemy described the action of light as it passed through glass:
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al-Haytham & Vision:
• al-Haytham was an Arabic scientist who studied light
• In about 1000 A.D., he correctly described how vision worked:
• al-Haytham also tried to explain how rainbows formed, but he experienced little success
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Newton & Light:
• Sir Isaac Newton studied many aspects of physics and mathematics
• One major contribution that he made was the discovery of the components of white light:
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The Speed of Light
• Scientists knew that light would travel in straight lines, but they had no idea how fast it traveled
• The main problem is that old clocks and timing instruments were not accurate enough to measure the high speed at which light traveled
• There are two solutions to this problem:
1.
2.
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Ole Romer
• Ole Romer used a very large distance to determine the speed of light in 1676:
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Albert A. Michelson’s Experiment:
• In the 1920s, Albert A. Michelson developed an experiment that gives us the currently accepted value for the speed of light (300 000 km/s or 3.00×108 m/s):
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Some Properties of Light
• Light has some basic properties:
1.
2.
3.
4.
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1.2 – Optical Devices
• Optical Device:
• Many optical devices have improved our lives by improving medicine, and by letting us see far into the universe
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Microscopes
• Hans and Zacharias Jansen built the first microscope in 1595
• This first microscopes were relatively simple, but led to incredible discoveries
• In the 17th century, Antoine van Leeuwenhoek studied many things under his microscope
• He made the first observations of many cells and organisms, such as:
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How a Microscope Works:
• Microscopes use a series of lenses to magnify an object
• Recall that the image produced by a microscope is upside-down and backwards
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Telescopes
• Single lenses provided a little closer view of the stars and planets
• However, the invention of the telescope in the Netherlands in the 17th century revolutionized astronomy
• Galileo built his own telescopes to study the stars
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Galileo’s Discoveries:
• Galileo discovered a number of important things about our solar system using his telescope:
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Types of Telescopes:
• Telescopes come in two types:
1. Refracting Telescopes
2. Reflecting Telescopes
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The Refracting Telescope
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The Reflecting Telescope
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Binoculars
• Telescopes can be bought for home use, but they are usually very large and heavy
• Binoculars are a smaller, lighter, and more portable solution
• They provide less magnification than a telescope, however
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How Binoculars Work• To
accommodate for their shorter length, prisms are used to redirect the light along a longer path in the binoculars