Download powerpoint Light 00

The nature of light!
What is light?!
Light acts like a wave (it is an electromagnetic
wave) http://www.phy.ntnu.edu.tw/ntnujava/viewtopic.php?t=52
  Light acts like a stream of particles
  Light is the only thing we can see
  Visible light is a small portion of the
electromagnetic spectrum
  Visible light ranges in wavelength from about 400
nanometers (nm) to about 760 nm
 
What is an electromagnetic
wave?!
  all
electrons are surrounded by an electric
field
  a wiggling electron will wiggle the electric
field
  a wiggling electric field will induce a
wiggling magnetic field
  a wiggling magnetic field will induce a
wiggling electric field
  get it? It keeps going and going!
The electromagnetic spectrum!
Frequency corresponds to color and energy
  The higher the frequency, the more energy the
wave “packets” carry
  Highest frequency--hard gamma rays
  Ultraviolet--frequency just above the upper visible
violet. Infrared--frequency just below visible red.   Microwaves--resonant frequency with water
  Radio--large range of frequencies for info
transmission
 
EM Spectrum!
Light as a wave!
diffraction--will spread out after going through an
opening if the opening is small enough
  refraction--will bend if entering a different
medium at an angle
  interference--produces interference patterns just
like water and sound waves do
  can be polarized (made to vibrate in a single
plane)
 
Light as a particle!
can propagate in a straight line-(laser)
  is emitted in bundles called “photons”
  each photon is a particle-like packet, clump,
discreet amount, or quantum of light energy
(E=hf, h=Planck’s constant=6.62x 10-34 J s)
  higher intensity light (brighter) means more
photons
  higher frequency light means more energy per
photon
 
A wave and a particle?!
  How
can anything be a wave and a particle
at the same time?
  Particle-wave duality violates common
experience, yet is clearly evident at the
microscopic level
  Richard Feynman said “I think I can safely
say that nobody understands quantum
mechanics.”
Additional Tidbits!
em waves travel at 3 x 108 m/s in a
vacuum
  when em waves encounter a “medium” they
get slowed down
  the higher the frequency the wave, the more
dangerous it is, and the more dense a
material it can go through
  all
Wave Nature of Light!
  Young’s
Double Slit Interference
Experiment
  We will collect data in class
  Make all calculations on the HW sheet
  Read Microscopic Weirdness & answer
questions
  Read and take notes from Giancoli section
24-3 (p. 727 – 730)