early concepts of light (wrong!!) ancient greece –some believed light consisted of particles that...
TRANSCRIPT
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?
• Greek Philosopher/Scientist, Empedocles, was the first to teach that light traveled in waves– Wave Theory was accepted by nineteenth
century
Instantaneous or Finite Speed?
1675 - Danish Astronomer, Olaus Roemer was the first to demonstrate that light traveled with a finite speed!!!
How Fast?
• American Physicist, Albert Michelson (1880)
• Winner of the 1907 Nobel Prize
• Determined speed to be 299,920 km/s
Light &
Electromagnetic Waves
Light Fundamentals
• Light - An Example of a Transverse Wave
• Speed of Light 3.0x 108 m/s
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
Light Sources
• Light Sources– luminous vs. illuminous
• emits light vs. reflects light
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
Light Fundamentals
• Illuminance, E – The illuminous Intensity of a surface
• Measured in lumens per square meter or a lux, lx)
• E = P / 4r2
Light and Matter
• Transparent Materials– Materials that allow
light to pass through them in straight lines.
Light and Matter
• Translucent Materials– Materials that transmit
light but do not allow objects to be seen clearly through them.
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
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