PROPERTIES OF LIGHT

• A radiant energy emitted directly or indirectly by objects, and it affects the eyes

  Light
• Sources of Light

  • Natural Source (Sun, stars, lightning, fireflies)
  • Artificial Source (Lamps, bulbs, burning of wood or other materials)
• 
  

  Also known as theory of emission, developed by Isaac Newton (1665), light was made of tiny particles called corpuscles that comes from a source with certain velocity that travels in space and produced sensation of sight when they struck the eye

  Corpuscular Theory
• 
  

  Wave Theory

  Sometimes called undulatory theory, developed by Christian Huygens (1667), the propagation of light is like the motion of waves in matter, light is made up of waves that comes from vibrating body that travels in space
• 
  

  • Discovered polarization, invented the lens used in lighthouses around the world

  
  

  Fresnel(1817)
• • (1773-1829)Worked on the diffraction and interference of light
  • Thomas Young
• • Measured the speed of light in water to be ¾ of that in air
  • 
    
  • Jean Foucault (1850)
• • Developed the Electromagnetic Theory, light was an electromagnetic phenomenon, a succession of waves produced by periodic variations of two vectors, the electric and magnetic intensities, accompanied by a vibrating charge
  • James Clark Maxwell (1864)
• • Developed Quantum Theory, believed that radiant energy was transported in the form of discrete particles called Quanta
  • Max Planck (1858-1947)
• • Light is composed of bundles of wave energy called photons (agreed on Planck's findings)
  • Albert Einstein (1879-1955)
• • Photons of X-ray decreased in energy when colliding with electrons
  • Arthur Compton (18-92-1962)
• • Extend the possibility of proposing matter can have wave properties
  • Louis de Broglie (1892-1987)

  
• Speed of light


  300,000km/s in space, 197,000km/s in glass
• Wavelength of light


  From 400nm to 700 nm in length
• Nanometer (nm)


  One billionth of a meter (1 x 10-9)
• What happens when light strikes an object

  • Absorbed (transferred to the object, mainly as heat)
  • Reflected (bounces off, such as with a mirror)
  • Transmitted (goes through, such as with glass)
• Classification of objects by what they do to light

  • Opaque (does not allow light to pass through, all light is either absorbed or reflected)
  • Translucent (can be seen through, but not clearly, allows some light to go through, but some is also absorbed or reflected)
  • Transparent (allows almost all light to go through, so can be seen through clearly)
• White light


  Made up of all the colors of the rainbow

  
• A prism splits ______ into its component colors

  
  

  
  

  White light

  
• How we see colors

  We see the color of light being REFLECTED from an object
• Examples of how objects create color

  • Blue object reflects blue light and absorbs all others
  • Black object absorbs all colors of light and doesn't reflect any
  • White object reflects all light and absorbs none
• Subtractive color system


  Uses colorants (dyes or pigments) to subtract portions of the white light that is shining on the object, the colors are cyan, magenta and yellow
• Additive color system


  Involves light emitted directly from a source before an object reflects light, a TV screen or computer monitor creates color using the primary colors of light: red, blue and green
• Primary colors of light

  • Red
  • Green
  • Blue
• Secondary colors of light

  • Magenta (red + blue)
  • Cyan (blue + green)
  • Yellow (red + green)
• Mixing the primary colors of light (red, green, blue) = white light</b>

  
• Types of reflection


  • Regular (smooth surface, see an image)
  • Diffuse (rough surface, no image)
• Refraction


  Light slows down as it goes from space to air, and even more in water and glass, because the atoms get in the way
• Lenses


  Clear, curved transparent objects used to bend light
• Convex (positive) lenses


  Converge (focus) light and can form images
• Concave (negative) lenses


  Diverge (spread out) light rays

  
• Total internal reflection


  When light strikes a boundary between two transparent materials at the correct angle, all the light gets reflected, this is how fiber optics works
• Laser


  Light amplification by stimulated emission of radiation, uses one wavelength of light with all the crests and troughs lined up, used for welding, cutting, reading/writing CDs, transmitting data, and as pointers
• The normal line is an imaginary line perpendicular to the surface at the point where the light ray strikes it.
• Refractive index (n) is defined as the ratio of the speed of light in vacuum to its speed in a material.
• Refraction occurs when light changes direction as it passes from one medium into another with a different density.
• Light travels at different speeds through different materials due to refraction.
• White light can be separated into its component colors using a prism or a diffraction grating.
• Prisms can be made out of glass or plastic and are commonly used to separate white light into its constituent colors.
• Snell's Law states that the incident angle equals the refracted angle multiplied by the refractive indices of the media.