Short notes on Polaroid

A Polaroid is a physical device used to filter light rays. It is the systematic arrangement of lenses. When light rays pass through the polaroid, only half of the total rays pass through it and the remaining half get reflected into the surrounding area. The Polaroids are manufactured artificially by the suitable arrangement of lenses. Although, when the light passes through the polaroid, its intensity changes. In most cases, it decreases compared to the unpolarized light. 

Tourmaline crystal

Tourmaline crystal is a group of boron silicates used to produce polarized light. The tourmaline crystal contains two refracting surfaces. Both the surfaces absorb the same amount of light. One refracting surface refracts light in a forward direction, which passes out from the polaroid and is called polarized light. Another refracting surface refracts the light in a backward direction, which reflects from the polaroid and is called unpolarized light. So, the tourmaline crystals are used to prepare the internal mechanism. 

Selective absorption

The phenomenon of selective absorption is also called dichroism. In this phenomenon, those light waves whose electric field is vibrating in a plane get transmitted, which is parallel to the direction of the orientation of light. The not parallel waves in the orientation direction either get absorbed by the material or get reflected into the surrounding area. This phenomenon is used for producing polarized light. All the polaroids and polarizers are based on this phenomenon. 

Half of its rays remain in the parallel orientation direction when any light passes and the other half remain in the perpendicular orientation direction. So, the material (which shows a property of selective absorption) passes the rays in the parallel orientation direction and reflects the rays in the perpendicular orientation direction. In the same way, all the polaroids and polarisers work. 

Discovery of polaroid 

Polaroids are artificially prepared dichroic materials. The great scientist W. H. Herapath artificially invented the crystalline material called iodosulfate, extracted from quinine. He named this discovered material herapathite. Herapathite shows the phenomenon of dichroism. Later in 1934, another great scientist named E. H. Land arranged these herapathite crystals in the cellulose acetate. He placed all the crystals with the optic axis parallel to cellulose acetate. After that, a layer was formed and inserted between the two glasses for protection. It resulted in the formation of sheets that polarized the light. This mechanism is called a polaroid. Polaroid is used widely for producing polarized light. 

Uses of Polaroids 

Polaroids are used extensively for producing polarized light. The material or sheet used in the manufacturing of polaroids is prepared artificially. Now, let’s take a look at some uses of polaroids. 

• The light from the sun gets scattered in all directions on earth. The surface of the earth is small in comparison to the surface of the sun. So, the amount of light coming from the sun is much higher than the earth’s total surface area. So, a large amount of light is reflected at any instant on the earth’s surface. The intensity of this light is very high, which sometimes impacts the vision of any individual. So, these polaroids are used in sunglasses, where they restrict the entry of glared reflected light and protect the eyes of human beings.
• An airplane flies high in the sky. The intensity of sunlight is very high in the upper layer of the earth, where planes fly. So, polaroids are used in the windows of airplanes to reduce the intensity of sunlight entering the aircraft. 
• Polaroid is used to enhance the experience of three-dimensional movies and pictures.
• Polaroid is used as a filter in the cameras. It is also used in the cameras of mobiles. 
• Polaroid is also used in liquid crystal displays. They are used in calculators, monitors and watches which contain LCD screens. 

Conclusion 

Polaroid is extensively used in the production of polarized light. All the polaroids are based on the phenomenon of selective absorption. Half of the light rays get reflected into the atmosphere and half get passed from the material (used for selective absorption). When any lights get polarized, their intensity and wavelength both get changed. The power of light decreases, due to which they are used in sunglasses to prevent harmful rays of the sun. They are also used to filter the intensity of light while capturing the images from a camera.