Nicol prism and its significance in double refraction

It is the most common polarizing prism. Nicol prisms were used to measure the polarization angle of birefringent compounds. These prisms are useful in the understanding of interaction between polarized light and crystalline substances. This interactive tutorial explores the orthogonal or mutually perpendicular waves as the result of light transmission through a Nicol prism. A typical Nicol prism is composed of a doubly refracting material, usually calcite. When a beam of white unpolarized light enters a crystal of this type the beam is separated into two components that are polarized in mutually perpendicular directions. One of these light rays is called as the ordinary ray, while the other is called the extraordinary ray. The ordinary ray is refracted to a greater degree in the birefringent crystal and impacts the cemented surface at the angle of total internal reflection. As a result, the ordinary ray is reflected out of the prism and eliminated by absorption in the optical mount. The extraordinary ray traverses the prism and emerges as a beam of linearly polarized light that is passed through the substage condenser directly to the specimen. Nicol prisms cannot be used at high magnifications as it has a limited aperture. Nicol prisms are very expensive and bulky. Instead, polarized light is now most commonly produced by absorption of light having a set of specific vibration directions in a dichroic medium .Any device capable of selecting plane-polarized light from natural white light is now referred to as a polar or polarizer. Today, polarizers are widely used in LCDs, sunglasses, photography, microscopy, and for a myriad of scientific and medical purposes.

Posted in: