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Unit 3 Light and Optical Systems

Unit 3 Light and Optical Systems. Topic 1 What is Light?. Have you ever asked yourself, “What is light?” or, “I wonder what light is?” Maybe you asked yourself, “Geez, what would light be?” Or…maybe you never asked yourself these questions. But I bet you did. Crazy monkeys!.

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Unit 3 Light and Optical Systems

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  1. Unit 3 Light and Optical Systems Topic 1 What is Light?

  2. Have you ever asked yourself, “What is light?” or, “I wonder what light is?” Maybe you asked yourself, “Geez, what would light be?” Or…maybe you never asked yourself these questions. But I bet you did. Crazy monkeys!

  3. Lightis the form of energy you can see; it can beproduced naturally by the sun or fire, or artificially by light-producingtechnologies, like batteries.

  4. Radiation is the wave-like transfer of light, from its source, in all directions. Lightis often called radiant energy. Light from the sun is formed by nuclear fusion.

  5. Less than one millionth of one percent (0.00000001 %) of the sun’s energy actually reaches earth!

  6. The 1st Basic Principle of Light When light reaches a surface,it can beabsorbed and transformed into other types of energy…

  7. electrical energy(solar cells change light into electricity) • thermal energy (a road absorbs light in the summer, making it hot) • chemical energy(trees absorb sunlight and make sugars)

  8. The amount of energy a surface receives depends on the intensityof the light. The more intense the light, the more light can be absorbed. (think of the temp. of a hot road on a sunny day, versus the temp. of the road on a cloudy day)

  9. NATURAL LIGHT SOURCES Sun, Fire (wood), Candles and Oil Lamps Bioluminescence – light produced by living organisms.

  10. Because sunlight is not always available, we have developed artificial light sources.

  11. Artificial Light Sources Incandescent – heat causes a metal filament to glow Fluorescent – ultraviolet lights (high-energy) are absorbed by particles and then emitted Phosphorescent – same as fluorescent, but light is emitted over time rather than immediately.

  12. Chemiluminescent – light released by chemical reactions

  13. The Cost of Lighting Electrical energy costs money to produce. A wattis a unit of electrical power. The cost is calculated by how much of the electrical energy is used over a certainperiod of time.

  14. Calculations are made in kWh’s. 1 kWh is 1000 watts ofelectrical energy operating for 1 hour. Example: Calculate the cost of leaving a 60W light bulb on for 10 hours.

  15. Step 1 - Convert 60W to kW by dividing by1000: 60 W / 1000 = 0.06 kW Step 2 - Calculate the number of kW hours: 0.06 kW x 10 hours = 0.6 kW.h Step 3 - Calculate the cost by multiplying thenumber of hours by the cost per kW.h

  16. If the cost per kW.h is $0.08, the cost of electricity to operate the 60W light bulb for 10 hours would be: 0.6 kW.h x $0.08 = $0.048 (4.8 cents – or about 5 cents)

  17. The Ray Model of Light ‘Light travels in straight lines’ A ray is a straight line that represents the path of a beam oflight. The ray model helps to explain how shadows can be formed, when the rayof light is blocked by an object.

  18. Light travels in straight lines until it strikes a surface. The type of surface will determine how the light will continue.

  19. If the surface is transparent, the light continues in a straight paththrough the object If the surface is translucent, the light will be diverted (refracted)after it passes through If the surface is opaque, the light will be blockedand not allowed through the object

  20. Opaque Let’s play . . . Name that Surface!!! Translucent Transparent

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