Science 8 Unit C

1. Science 8 Unit C Light & Optical Systems

2. Unit C Section 1.0 Our knowledge about light and vision comes from explanations, inventions, and investigations.

3. 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

4. 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

5. 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:

6. Problems With Pythagoras’ Theory:

7. Euclid & Ptolemy: • Euclid discovered two important properties of light: 1. 2. • Ptolemy described the action of light as it passed through glass:

8. 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

9. 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:

10. 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.

11. Ole Romer • Ole Romer used a very large distance to determine the speed of light in 1676:

12. 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):

13. Some Properties of Light • Light has some basic properties: 1. 2. 3. 4.

14. 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

15. 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:

16. 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

17. 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

18. Galileo’s Discoveries: • Galileo discovered a number of important things about our solar system using his telescope:

19. Types of Telescopes: • Telescopes come in two types: • Refracting Telescopes • Reflecting Telescopes

20. The Refracting Telescope

21. The Reflecting Telescope

22. 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

23. How Binoculars Work • To accommodate for their shorter length, prisms are used to redirect the light along a longer path in the binoculars