auroras
TRANSCRIPT
AurorasPaintings in the Sky
Lokhaze Ali
Aurora
• Meaning of Aurora is Dawn, Daybreak or Sunrise
• Aurora was the Roman Goddess of Sunrise
Roman Goddess AuroraAurora (painting the dawn)Just before the sun rises there is a hush all over the land in anticipation of the arrival of Aurora the Goddess of dawn. Using her rainbow coloured palette she paints the sky and clouds with the dramatic colours and light of the imminent dawn, until with a burst of brightness the sun emerges and another day begins. Her work is never done as she travels the world painting a million dawns in a continuous cycle. With each dawn comes a new day to celebrate and enjoy.
Creation of Auroras
• Auroras are caused by the bombardment of solar electrons on oxygen and nitrogen atoms. The electrons literally excite the oxygen and nitrogen atoms high in the atmosphere to create the beautiful light show we know as an aurora.
What causes an Aurora?
Auroras
• http://www.nasa.gov/multimedia/videogallery/index.html?media_id=97423582
Polarization
• Polarization is a property of certain types of waves that describes the orientation of their oscillations. Electromagnetic waves, such as light and gravitational waves exhibit polarization.
• By convention, the polarization of light is described by specifying the orientation of the wave's electric field at a point in space over one period of the oscillation.
Linear polarization
The two orthogonal (perpendicular) components are in phase. In this case the ratio of the strengths of the two components is constant, so the direction of the electric vector (the vector sum of these two components) is constant. Since the tip of the vector traces out a single line in the plane, this special case is called linear polarization.
Circular PolarizationThe two orthogonal components have exactly the same amplitude and are exactly ninety degrees out of phase. In this case one component is zero when the other component is at maximum or minimum amplitude. There are two possible phase relationships that satisfy this requirement: the x component can be ninety degrees ahead of the y component or it can be ninety degrees behind the y component. In this special case the electric vector traces out a circle in the plane, so this special case is called circular polarization.
Elliptical Polarization
• Another case is when the two components are not in phase and either do not have the same amplitude or are not ninety degrees out of phase, though their phase offset and their amplitude ratio are constant. This kind of polarization is called elliptical polarization because the electric vector traces out an ellipse in the plane (the polarization ellipse).
Polarized Effect
A polarizer filters out the polarized component of light from the sky in a color photograph, increasing contrast with the clouds (right).
