1. Fundamentals of Light

2.  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.  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 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/m 2

5.  The amount of light that hits a surface depends on the distance to the object.  In fact it is an…..

6. 9090

7.  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.  Michelson’s measure of 2.997996 x 10 8 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 10 8 m/s  Light travels 9.46 x 10 12 km in one year.

9.  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.  Newton used a prism to pass white light through.  Newton called this arrangement of colors a spectrum.

11.  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. A. 4.28 x 10 14 Hz B. 4.9 x 10 8 Hz C. 4.28 x 10 5 Hz D. 4.9 x 10 -1 Hz

13. A. Red, blue, yellow B. Red, blue green C. Magenta, cyan, yellow D. Magenta cyan, green

14.  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. Red BlueGreen Magenta Yellow Cyan

16.  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.  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.  The primary pigments are Cyan Magenta Yellow  Each pigment only reflects the color of light it is made of.

19. A. red B. green C. blue

20.  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.  Why do we buy polarized sunglasses?  What exactly does it mean that they are polarized?

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

24.  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.