Probability Amps

(Created prior to 1993)
  
Question:  How do physicists determine the direction of probability amplitude 
for all types of light?  I know that red light has a rotation of about 36,000 
times per inch traveled.  Does this have any relation to the frequency of this 
light?
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Yes, your number 36,630 is the number of wavelengths of red light 
in an inch.  The wavelength times the frequency is equal to the speed of 
light, so there is an indirect relationship to the frequency.  For my number I 
assumed that the wavelength of red light is 7000 angstroms.  The frequency 
would be 4.2 times 10 to the 14th power.  Probability amplitudes are something 
different.

Sam Bowen
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The relation between the wavelength of light and its frequency is  
given by:  wavelength * frequency = speed of light (=300,000 km/second).  So, 
for visible light, which covers wavelengths from 400 to 700 nanometers (4 to 7 
X 10^-7 meters, or 1.5 to 2.7 X 10^-5 inches) the frequencies go from 7.5 to 
4.2 x 10^14 Hertz (1 Hertz = 1 cycle per second).  More on the human scale are 
radio stations - for example, an FM station at 100 Megahertz (a frequency 
which can be generated by ordinary electronics has a wavelength of:  3 x 10^8 
meters/second/1 x 10^8 Hz = 3 meters.  The ideal antenna for picking up radio 
signals is about one half of a wavelength, or about 1.5 meters (= 5 feet) for 
this frequency which, if you think about it (think of a car antenna), is about 
the size people actually use!  For our radio station, the radio waves, like 
light, are known as "electro-magnetic" waves, and have electric and magnetic 
fields associated with them (That is why you can generate them with an 
electrical circuit).  An electric field is something that causes an electrical 
charge to move in the direction the field is pointing, and similarly a 
magnetic field causes a magnet to orient itself along the direction it is 
pointing.  So, at any instant, the radio waves have a certain collection of 
these electric and magnetic fields spread out all over the place.  Imagine 
freezing this collection of fields, and testing the directions while moving 
towards and away from the station transmitter.  What you will find is that 
first of all the fields are always pointing perpendicular to the line-of-sight 
from the transmitter (they never point along the direction they are going) and 
that the electric field is always perpendicular to the magnetic field.  You 
will also find that every 1.5 meters (1/2 of a wavelength) both the electric 
and magnetic fields flip direction, so that after a full 3 meters, they are 
back where they started again.  That is why they are called waves!  Now 
unfreeze it.  1 of over the frequency is 10^-8 seconds, which is called the 
period.  You will find that every 1/2 period (5 x 10^-9 seconds) in time, the 
electric and magnetic fields everywhere flip directions, so that after a full 
10^-8 seconds, they are again back where the started.  So the frequency (100 
million inverse seconds) is the number of times a second the fields do one 
full cycle.  The same (much faster and smaller) is true of light.

Arthur Smith
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