Polarized Sun Rays
Light wave has two components, the magnetic and electric components. These components are mutually perpendicular. The electric component forms the plane of oscillation for the wave. When an atom emits light wave in a single event, such wave has a fixed plane of oscillation. When several atoms emit light waves, the waves may not have same plane. Sun ray consists of various light waves, each with different planes of oscillation, and there is a random change in the light’s direction. This kind of light is unpolarized.
When light is polarized, the waves come in with the electric and magnetic field vectors in a defined direction. In a light wave, the electric field vibrates in a perpendicular direction to the ray. For an unpolarized incident sun ray, the electric field vibrates randomly in a plane perpendicular to the ray. The vibration of the electrons of the scattering molecules is also confined to that plane. When viewed from the side of the plane (900), the vibrations seem to be confined in a line. Therefore, light scattered at 90 degrees is linearly polarized.
Sun rays are polarized due to the scattering by the electrons in molecules of air. The electrons vibrate in perpendicular directions to the sun rays and reradiate light in a direction perpendicular to the electron’s motion. Therefore, sun rays coming directly at noon are unpolarized. However, the polarization increases as one looks in directions perpendicular to the rays. There is maximum polarization at sunset when one looks straight up in directions perpendicular to the rays of the sun. However, the rays are never fully polarized since some light are scattered severally before reaching the eyes.
Works Cited
Können, G. P. Polarized light in Nature, Cambridge University Press, 1985.
Polarization.com. Riding to a Polarized Sunset. Web. 1 July 2012. http://www.polarization.com/sky/sky.html
