Fun Physics You Can See

1
Fun Physics You Can See

• Lasers, Holograms and Spectroscopy

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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.

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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.

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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.

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Spectroscopy The Finger Prints of Elements

• Spectroscopy is the study of the spectrum from
  different atoms and molecules.

• 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.

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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 short wavelength.

• 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.

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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!

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Fun Facts

• A hologram the size of a sugar cube could hold
  enough information for about 30 DVD movies!
• CDs, 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!