Chapter 5: Periodicity and Atomic Structure
In this chapter you will get a
modern understanding of the atom. Much of them came from an
understanding of how light interacts with matter. First we will
explore the nature of light, followed by its interaction with matter,
and then a new
description of electrons and electron arrangement around nuclei.
Intro to Light:
For these links get a sense of
some properties of light.
EM spectrum: visible
light is small part of the entire electromag. spectrum
A prisms bends light of different wavelengths
to different degrees, allowing "white" light to be separated into its
Index of Refraction:
Different media bend light
Diffraction Grating 2 |
CD - diffraction grating:
Gratings (numerous slits
etched in a transmitting or reflecting surface) can also separate light into
its component wavelengths, much like a prism.
Intro to Waves: Types and Properties
- TYPES OF WAVES
The water and EM waves below
are example of transverse waves - the disturbance is perpdenicular to the
direction of propagation of the wave
You've done this a a kid.
Circular water waves emanate from the point of disturbance. Note the
propagating lighter/darker regions. These reflect the crest/trough of
the wave (or depending how the movie was made, the trough/crest.
light as two mutually perpendicular waves -
one an oscillation in the electric field, and one in the magnetic field
- PROPERTIES OF WAVES I:
What do waves do? They
reflect, refract (see above) and diffract (bend around corners). When
to waves meet, they add to each other in ways that produce constructive
interference - when peaks arrive simultaneously, or destructive interference
(when a peak and trough arrive simultaneously). When the combine or
"superimpose" they produce an interference or diffraction pattern. The
links below demonstrate these ideas.
Wave Reflection, Fixed End
Wave Reflection, Open End
of Waves :
vTwo sinusoidal waves approach and
superimpose (through simple addition of the wave) to form a new resultant
the top two waves can be varied by dragging
the balls to produce a new wave form (lower left). Again constructive and
destructive interference results in a new wave which is simply the
superposition (addition) of the two waves.
Two Water Waves
to the single water wave above, you will see two water waves superimposing.
you should see rays emanating from the combined waves showing where
the combined waves destructively interfered to produce little observable
trough and peaks and rays with constructive interference. This is also
seen in the Two Slit link below
Wave Interference 1
Wave Interference 2
Wave Interference 3
Two slit interference
This is a pictorial representation that shows
the same rays of destructie (-) and constructive (+) interference see in the
Water Waves above. Think of the purple circles as the peak of
- Laser through single slit:
- if slit infinitesimal point, light passing through
emanate in a cone-shaped volume, as if light emitted in all directions
through slit (no diffraction pattern ).
- If slit is very wide, there is no diffractions and light goes
straight toward detector.
- If the slit width is similar to wavelength of life, get diffraction
pattern as if multiple point "slits" existed
Another two slit demo
An animation of light passing through slits,
analagous to the Two Water Wave experiment
X Ray Crystallography
Classical Physics and the Demise of the
Wave Nature of Matter: Quantum
Quantum Theory and Electronic Structure
- Quantum Behavior of C70. Science.
292. pg 1471 (2001)
- Electronics vs Spintronics: Nature 411, pg 747
- The Fog That Was Not (Femtosecond resolution and
uncertainty) Nature, 412,pg 279 (2001)
- Zeilinger. The quantum centennial: One
hundred years ago, a simple concept changed our world view forever.
Nature. 408, pg 639 (2000)
- Schrodiner's Cat is out of the Hat. Science.
290. pg 720, 773 (2000)