Birefringence, also known as double refraction, occurs in optically anisotropic crystals, where a ray of light is broken into two waves that pass at different speeds. Tourmaline, calcite, ice, and quartz are birefringent. Birefringence can be used in optical filters and scientific experiments. Glasses and glass can also demonstrate birefringence.
Birefringence is a property exhibited by certain types of crystal structures in which a ray of light passing through the crystal is broken into two unequal waves which pass at different speeds. This property is also known as double refraction. In a classic example of how birefringence works, if a piece of birefringent material is placed on a piece of paper with a dot, two versions of the dot will appear. Tourmaline, calcite, ice and quartz are all birefringent in nature.
This property occurs when a crystal is optically anisotropic. When something is said to be anisotropic, it means that its properties can vary depending on the direction of measurement, rather than something that is isotropic, in which case the properties will be the same from all angles. In the example above with a birefringent crystal block placed on top of a piece of paper with a dot, as the paper is rotated, one of the dots will move, because the refractive index changes with angle.
In birefringence, two waves of light are generated. The first is the ordinary wave, and will remain fixed in direction, with the light passing straight through the crystal without interruption. The second wave is known as the extraordinary wave and moves when the crystal is rotated. The extraordinary wave surrounds the ordinary wave, changing as it hits different areas of the crystal and refracts differently. This is because the polarization of light changes as the object is reoriented.
This property can be put to a number of interesting uses. Birefringent optical filters can be installed on a variety of devices to take advantage of birefringence, for example. Specialized birefringent glass products are used in various scientific experiments and industrial processes, and calcite is also commonly used in applications where birefringence is desired. It is also possible to see trirefractive materials, in which there are three refractive indices.
People who wear glasses can explore birefringence by experimenting with the edges of the lenses. When the glasses are positioned correctly, it should be possible to break up an image into a doubled pattern, caused by the different refractive indices found along the edges of a pair of glasses. Birefringence can also be demonstrated with many types of glass; as the glass moves, the refractive indices should change, making ordinary and extraordinary rays visible in the form of a moving double image.
Protect your devices with Threat Protection by NordVPN
