Light!

Don’t forget that light travels faster than sound . . . that’s why so many people appear bright

until they speak.

Particle or wave?“There is no knowledge, no LIGHT, no

wisdom that you are in possession of, but what you have received it from some source.”

Brigham Young

1801-1877, American Mormon Leader

Particle or wave?• Light is a particle (“corpuscular”) !

– Newton

• Light is a wave!– Huygens

• Max Planck, 1900:– How does emitted radiation relate to temp?– Mathematical “fudge factor”

• Assumed energy (I.e., temperature) was chunked, discrete, not a continuous function

Light production

But, soft! what light through yonder window breaks? It is the east, and Juliet is the sun. Arise, fair sun, and kill the envious moon, Who is already sick and pale with grief, That thou her maid art far more fair than she:

- W.Shakespeare, Romeo and Juliet

. . . and there is light.

Light production

• Bohr model– Incident photon excites electron to higher

energy level– Electron drops to lower energy level,

emitting photon– Jump size proportional to photon energy

• Animation• But it gets even better . . .

. . . and there is light.

The stuff of Nobels

“An age is called Dark not because the LIGHT fails to shine, but because people refuse to see it.”

James A. Michener 1907-, American Writer

The stuff of Nobels

The stuff of Nobels• Einstein

– Light is quantized– Photoelectric effect

Energy of emitted photons depended on frequency of incident light, NOT intensity

– Physics Nobel, 1921

• Wavicles!

The stuff of Nobels

“Out of compassion I destroy the darkness of their ignorance. From within them I LIGHT the lamp of wisdom and dispel all darkness from their lives.”

Bhagavad Gita

c. BC 400-, Sanskrit Poem Incorporated Into the Mahabharata

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“Thy word is a lamp to my feet, and a LIGHT to my path.”

[Psalm 119:105] Bible

“Thousands of candles can be lighted from a single candle, and the life of the candle will not be shortened. Happiness never decreases by being shared.”

Buddha

“There are two kinds of light -- the glow that illumines, and the glare that obscures.”

JamesThurber, American author

Mathematics . . .

"The good Christian should beware the mathematician and all those who make empty prophecies. The danger already exists that the mathematicians have made a covenant with the devil to darken the spirit and to confine man in the bonds of hell.” - St. Augustine

Mathematics

Mathematics . . .

• Speed of a wave = frequency x wavelength

c = • Energy of light = Planck’s constant

x frequencyE = h

Planck’s constant = 6.626 x 10-34 Js

Mathematics

Polarization by TransmissionPolarization by Transmission

Polarization by ReflectionPolarization by Reflection

Polarization by ScatteringPolarization by Scattering

Dark Suckers - conceptual• http://

www.math.buffalo.edu/~sww/ZAP/index.html

• A new candle has a white wick. You will notice that after the first use, the wick turns black, representing all the dark which has been sucked into it. If you hold a pencil next to the wick of an operating candle, the tip will turn black because it got in the path of the dark flowing into the candle.

Dark Sucker “Theory”• This intrinsic darkness is bound into the electrons

of the surface material. • The reason host materials get warmer as they

release their intrinsic darkness is that there is a binding energy between darkness and its host material.

• Incidentally, the retinas of your eyes contain special pigments that send signals to your optic nerves when dark is sucked out of them — sucking out yellow-frequency darkness is experienced as seeing yellow light.

• http://home.netcom.com/~rogermw/darksucker.html

Dark Sucker “Theory”• Eventually, the surface can become so hot that it

glows with incandescence, and becomes a dark sucker itself.

• It should be noted that objects which glow due to their own heat, called "blackbody radiation", always cool off as a result of this radiation. This cooling off is merely the darkness being sucked into the blackbody radiator (hot dark sucker) and making the dark sucker itself into the darkness's new host material.

• The darkness-to-new-host binding process consumes heat to form its new bonds, each of which has its own binding energy, and the blackbody gets colder as a result.

• Chapter 14, sections 1 & 4

• p. 523, 1-6; p. 525, #1-3;

• p. 550+, 1-13,37-45

• Color mixing lab