Fun Physics You Can See

1. Fun Physics You Can See Lasers, Holograms and Spectroscopy Visit www.worldofteaching.com For 100’s of free powerpoints

2. The Inside Scoop on Light • Light is a wave, kind of like a wave in the ocean • These light waves carry energy. This energy can do many interesting things, like help grow a plant, produce electric currents, or cause chemical reactions. • Light carries a different amount of energy depending on its wavelength.

3. Wavelength: the Secret to the Rainbow • Light that has a longer wavelength appears more red, and light that has a shorter wavelength appears blue. • The shorter the wavelength, the higher the energy carried by the wave. • You may have heard of “ultraviolet” or “infrared” light. That is light at either extreme of wavelength, very short (ultraviolet) or very long (infrared). • Our eyes cannot always detect light if the wavelength is very long or very short.

4. Diffraction Gratings: The Bending of Light • A wave is bent when it hits a rough surface or passes through a small opening, or aperture. This is called diffraction. Diffraction happens to all types of waves, including light. • The white light we see from the sun and light bulbs is not really white. It is made up of many different colors. These colors that make up the light are known as a spectrum. If you have ever seen a rainbow, then you have seen the visible spectrum. • Diffraction gratings separate light into the different colors of light that it is made of.

5. Spectroscopy: The Finger Prints of Elements • Electrons in an atom can get excited. An excited electron is in a state of high energy. Sometimes these electrons jump down to a state with low energy. The difference in energy is given off as light. • Since different kinds of light have slightly different spectra, scientists can use a star's spectrum to figure out what elements it is made of. • Spectroscopy is the study of the spectrum from different atoms and molecules.

6. Phosphorescence: A Big Word for Glow-In-the-Dark Certain compounds contain things called phosphors. • Phosphors emit visible light when exposed to energy, like from ultraviolet light. They do this because of electrons jumping between energy states. • In order to give the electrons enough energy, you have to use light with a shortwavelength. • Some phosphors, like the ones in fluorescent lights, do not glow after the energy source is taken away. Those that continue to glow after the energy is taken away are called phosphorescent.

7. Light Can Carry a Lot of Information • Holograms and fiber optics are two methods of information transfer that use light. • Holograms are made using lasers to record a 3 dimensional object on a 2 dimensional surface, like a piece of paper. Our eyes see the object because of controlled use of diffraction. • Fiber optics is a method of sending information as light through a cable. This light signal can be changed to music, video and more!

8. Fun Facts • A hologram the size of a sugar cube could hold enough information for about 30 DVD movies! • CD’s, like holograms, use diffraction patterns to store information. • Light from the sun can be transformed into usable energy to power homes, cars and more. • Light at the far ends of the spectrum, like microwaves (far into the infrared) and gamma rays (far into the ultraviolet) have some very interesting properties. You could read about them in the library, or on the internet!