1 / 24

Chapter 16

Chapter 16. Fundamentals of Light. Ray Model of Light. Light is represented as a ray that travels in a straight path. The direction can only be changed by placing an obstruction in the rays path. Sources of Light. Luminous Sources: objects that emit light Sun, flash lights, candles

arnaud
Télécharger la présentation

Chapter 16

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 16 Fundamentals of Light

  2. Ray Model of Light Light is represented as a ray that travels in a straight path. The direction can only be changed by placing an obstruction in the rays path.

  3. Sources of Light • Luminous Sources: objects that emit light • Sun, flash lights, candles • Illuminated Sources: objects that are visible as a result of light reflecting off of it • Moon, bicycle reflector • Opaque, Transparent, and Translucent are all used to describe how illuminated sources are visible

  4. Luminous Flux Luminous Flux is the amount of energy that a light emits. Unit: lumen (lm) A typical 100-W bulb = 1750 lm Illuminance is the rate at which light hits a surface. Unit: lux (lx) Equivalent to lm/m2

  5. Illuminance Inverse-Square Relationship The amount of light that hits a surface depends on the distance to the object. In fact it is an…..

  6. If I am standing 3 meters away from a light source, by how much does the illuminance change if I walk to 1 meter away from the object? • 9 • 0

  7. The speed of Light • Light was initially thought to travel at an instantaneous speed. • Galileo was the first to hypothesize that light has a finite speed. • Ole Roemer (Danish astronomer) was the first to find that light did travel with a finite speed. • In 1926 an American physicist, Albert A. Michelson used a set of rotating mirrors to measure the speed of light.

  8. Speed of Light Continued • Michelson’s measure of 2.997996 x 108 m/s won him the Nobel prize in science. The first American ever to accomplish this. • Today the speed of light, c, is given by 299,792,458 m/s. • For calculation purposes, c = 3 x 108 m/s • Light travels 9.46 x 1012 km in one year.

  9. Wave Nature of Light • In 1665 an Italian scientist observed that the edges of shadows are not perfectly sharp. • From this observation he realized that light was diffracted like all waves. • In 1678 a Dutch scientist Christiaan Huygens used this observation to argue the wave nature of light.

  10. Color • Newton used a prism to pass white light through. • Newton called this arrangement of colors a spectrum.

  11. Color Cont. • Since light was now proven to act like a wave, the wave equation is now applicable to use with light. • The range of frequencies for light are

  12. What is the frequency of a red light whose wavelength is 700 nm? • 4.28 x 1014 Hz • 4.9 x 108 Hz • 4.28 x 105 Hz • 4.9 x 10-1Hz

  13. What are the three primary colors of light? • Red, blue, yellow • Red, blue green • Magenta, cyan, yellow • Magenta cyan, green

  14. Color Addition of Light • White light is composed off all the different colors of the spectrum. • However, a combination of three colors with the correct intensities will produce white light. • These three colors are Red, Blue, Green. • These colors are known as the primary colors

  15. Color Wheel Yellow Magenta Cyan

  16. Addition of Color • Cyan, Magenta, and Yellow are called secondary colors because each is a combination of two primary colors. • Complimentary colors are two colors of light that can be combined to make white light.

  17. Color by Subtraction • The colors of objects are not only determined by the colors of light they reflect but also the colors of light they absorb. • Dyes and pigments are used to make materials absorb different colors of light.

  18. Color Subtraction • The primary pigments are • Cyan • Magenta • Yellow • Each pigment only reflects the color of light it is made of.

  19. If a white light is shown on an object that is made of a cyan pigment, what color will not be reflected off the surface? • red • green • blue

  20. Secondary Pigments • A pigment that absorbs two colors of light is called a secondary pigment. • Example: green pigment will only allow green light to reflect, therefore canceling out red and blue • Note that the primary pigments are the secondary colors and the secondary pigments are the primary colors.

  21. Polarization of Light • Why do we buy polarized sunglasses? • What exactly does it mean that they are polarized?

  22. Polarization • Light travels as a transverse wave, which means it’s particles vibrate perpendicular to the wave motion. • Polarization of light means to limit the direction in which light is allowed to vibrate.

  23. Polariztaion • In the picture above, the polarizer acts like a doorway, only allowing light that is traveling in a specific direction through.

  24. Reflection • When light reflects off of any surface, the light is polarized along the plane of the surface. • Example: light reflected off a road becomes horizontally polarized • When you wear polarized sunglasses, this reduces the “glare” from the cars and the road in front of you.

More Related