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Early Concepts of Light (Wrong!!)

Early Concepts of Light (Wrong!!). Ancient Greece Some believed light consisted of particles that entered the eye to produce sight Plato & Socrates believed that eyes emitted “streamers” making contact with objects, allowing sight. Who got it right?.

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Early Concepts of Light (Wrong!!)

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  1. Early Concepts of Light (Wrong!!) • Ancient Greece • Some believed light consisted of particles that entered the eye to produce sight • Plato & Socrates believed that eyes emitted “streamers” making contact with objects, allowing sight

  2. Who got it right? • Greek Philosopher/Scientist, Empedocles, was the first to teach that light traveled in waves • Wave Theory was accepted by nineteenth century

  3. 1675 - Danish Astronomer, Olaus Roemer was the first to demonstrate that light traveled with a finite speed!!! Instantaneous or Finite Speed?

  4. American Physicist, Albert Michelson (1880) Winner of the 1907 Nobel Prize Determined speed to be 299,920 km/s How Fast?

  5. Light &Electromagnetic Waves

  6. Light Fundamentals • Light - An Example of a Transverse Wave • Speed of Light 3.0x 108 m/s

  7. Light Fundamentals • Light is electromagnetic radiation • Light is simply a form of Energy that travels as a transverse wave. • All electromagnetic waves travel at 3.0 x 108 m/s • More on the Electromagnetic Spectrum

  8. Light Sources • Light Sources • luminous vs. illuminous • emits light vs. reflects light

  9. Light Fundamentals • Inverse-Square Relationship • The illuminance of a body varies inversely with the square of the distance from the light source • Luminous Flux, P • rate at which light is emitted (measured in lumens, lm) • Luminous Intensity • the luminous flux that falls on one square meter

  10. Light Fundamentals • Illuminance, E • The illuminous Intensity of a surface • Measured in lumens per square meter or a lux, lx) • E = P / 4r2

  11. Light and Matter • Transparent Materials • Materials that allow light to pass through them in straight lines.

  12. Light and Matter • Translucent Materials • Materials that transmit light but do not allow objects to be seen clearly through them.

  13. Light and Matter • Opaque Materials • Materials that absorb or reflect light without remission and therefore allow NO light to pass through them. • Opaque materials often create shadows where light can not reach

  14. Light and Matter • Polarization of Light • The aligning of vibrations in a transverse wave, usually by filtering out waves of other directions • 3D movies… and other tricks… Demos

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