November 30, 2012
As time progresses, I have concluded my theory of lights being caused by a series of waves of vibrations in this ether, which are set in the motion by the pulsations and luminous body. I become more interested in the extraordinary rays of biaxal crystals. These crystals allowed me to deduced the law of reflection and refraction. I will now explain to you about the phenomenon of double refraction or also known as birefringence. Double refraction is an optical property in which a single ray of unpolarized light enters an anisotropic medium which is then split into two rays, each travelling in a different direction. One of the ray (extraordinary ray) would be bent or refracted at an angle as it travels through the medium, while the other ray (ordinary ray) passes through the medium unchanged. To make things easier, both rays follow parallel paths even though their planes of vibrations continue to be perpendicular.
To observe double refraction taking place, I would be comparing to materials, glass and calcite. Then I would draw a pencil mark on the sheet and cover it with a piece of glass so only one image will be seen. On the other hand, if I cover the same paper with a piece of calcite, the crystal would be oriented in a specific direction making the two pencil marks visible.