The term "double refraction" refers to the phenomenon that occurs when a light ray splits into two separate rays as it passes through certain materials, such as calcite crystals. The word is spelled dʌbəl rɪˈfrækʃən in IPA phonetic transcription. The "d" sound is followed by a short "u" sound, and the first syllable is stressed. The "f" sound is spelled with a "ph" because it comes from the Greek word "phainesthai," meaning "to appear." The final syllable is spelled with an "sh" sound despite the "s" because of the following "i" sound.
Double refraction, also known as birefringence, refers to a fascinating optical phenomenon in which light passing through certain substances is split into two separate beams upon entering the material, each beam following a different path. The process occurs due to the anisotropic nature of the material, which means that its refractive index varies with the orientation of the light passing through it.
The separation of light into two beams is a result of the material's ability to slow down one component or polarization of the incident light more than the other. As a consequence, instead of experiencing a single refractive path, the light is refracted into two separate paths with different velocities. This gives rise to the phenomenon known as double refraction.
The two beams resulting from double refraction have distinct polarization orientations, referred to as the ordinary ray and the extraordinary ray. The ordinary ray follows Snell's law of refraction, while the extraordinary ray does not. Additionally, the two rays travel at different speeds and often diverge or converge as they pass through the material. This property has numerous important applications, specifically in the field of polarized light microscopy and the creation of optical components such as polarizers.
Although double refraction predominantly occurs in natural crystals such as quartz, calcite, and tourmaline, it can also be induced in certain man-made materials through stress or strain. By understanding and harnessing the phenomenon of double refraction, scientists and engineers can explore its practical uses in a wide range of scientific and technological applications.
The word "double refraction" is composed of two elements: "double" and "refraction".
The term "double" comes from the Latin word "duplus", meaning "twofold", "double", or "doubled". It entered the English language through Anglo-French and Old French, where it was spelled as "dublé" or "double".
The word "refraction" originates from the Latin word "refractio", which is derived from the verb "refringere". "Refringere" is a combination of "re-" (meaning "back" or "again") and "frangere" (meaning "to break"). Therefore, "refraction" essentially means "the act of bending backward" or "the act of breaking the path".