Light waves and their properties Page 104 chpt 4 book O

 What is light?  What is color?  Does everybody see color the same? Mabey blue to you is green to me, maybe green to me is red to someone else. So how do we know that we all see the same color?

 Before we can answer these questions we need to know how light works.  1 st we need to be able to describe how light interacts with objects.  When light strikes an object 3 things can happen. The light can be reflected, transmitted, or absorbed.

 Who can describe transparency to me?  Transparent material : transmits most of the light that strikes it.  This means that the light passes right through without being scatered.  Examples. Clear glass, water, air.

 Translucent material scatters light as it passes through, you can usually see something but the object is blurred so you can see details.  Examples are wax paper frosted glass.

 Opaque materials reflect or absorb all of the light that strikes it. You cannot see through an opaque material because the light cannot pass through it.  Examples include wood, metals, Thick cloth. Anything you cant see through is opaque.

 Why are thing different color. how does color work? These are some of the things we are going to answer in this section.  Color of opaque objects depends on the wavelengths of light the object reflects. Ever opaque object absorbs some of the wavelength and reflects the other part of the wavelength of the light that strikes it.  THE COLOR OF AN OPAQUE OBJECT IS THE COLOR OF THE LIGHT IT REFLECTS.

 Lets look at the apples. Open your book to pg. 108 O

 The color of an opaque object is determined by the color it absorbs. But does it work the same for a transparent object?  The color of a transparent or translucent object is the color of the light it transmits. The color in the wavelength through a transparent or translucent object is the only color let through so it makes a color filter.  Example : a transparent piece of blue glass only allows blue to pass through, so things you look at through a piece of blue glass will look different because it only allows blue through.

 What are primary colors?  Three colors that can combine to make any other color. The three colors of light are red green and blue.  The three primary colors of pigment are yellow, magenta, cyan. Pigment and light are different in the way light work on them.  Light : when these colors are mixed they create white light,  Pigment : when these are mix they create black.

 Why?  Light: when combined in equal amounts the three primary colors of light produce white light. If combined in unequal amount they will produce different colors. Red+ green= yellow, yellow is called a secondary color because it takes two primary colors to make it. A primary and secondary color can combine to make white light these are called complementary colors.

 Pigments: are color substances that are used to color other materials; pigments absorb some colors and reflect others. Mixing colors of pigments will create new colors the more colors of pigment that are mixed the few colors of light are reflected and more are absorbed. The more colors you mix the darker the mixture looks, until you get to black. Cyan, magenta, and yellow are the primary colors of pigment and when mixed in equal amount you get black.

 Refraction can cause you to see something that isn't really there.  How many of you have put a stick into water and seen it “bend”. This is refraction.  Refraction: when light rays enter a medium at an angle, the change in speed causes the rays to bend, or change direction.  Index of refraction: is a measure of how much a ray of light bends when it enters that material.

 As we saw in class we can split white light into many different colors, but how does it work?  The longer the wavelength the less it is bent by the prism. Which wave is the longest?  Red.  Red has the longest so it is refracted the least; so it is at one end of the spectrum, what color has the shortest wavelength;  Violet. So violet is at the other end of the spectrum and all of the other colors are spread out according to their wavelength.