A travelling microscope is an instrument for measuring length with a resolution typically in the order of 0.01mm. The precision is such that better-quality instruments have measuring scales made from Invar to avoid misreadings due to thermal effects. The instrument comprises a microscope mounted on two rails fixed to, or part of a very rigid bed. The position of the microscope can be varied coarsely by sliding along the rails, or finely by turning a screw. The eyepiece is fitted with fine cross-hairs to fix a precise position, which is then read off the vernier scale. Some instruments, such as that produced in the 1960s by the Precision Tool and Instrument Company of Thornton Heath, Surrey, England, also measure vertically. The purpose of the microscope is to aim at reference marks with much higher accuracy than is possible using the naked eye. It is used in laboratories to measure the refractive index of liquids using the geometrical concepts of ray optics. It is also used to measure very short distances precisely, for example the diameter of a capillary tube. This mechanical instrument has now largely been superseded by electronic- and optically-based measuring devices that are both very much more accurate and considerably cheaper to produce.
Travelling microscope consists of a cast iron base with machined-Vee-top surface and is fitted with three levelling screws. A matallic carriage, clamped to a spring-loaded bar slides with its attached vernier and reading lens along an inlaid strip of metal scale. The scale is divided in half millimeters. Fine adjustments are made by means of a micrometer screw for taking accurate reading. Both vernier reading to 0.01mm or 0.02mm. Microscope tube consists of 10x Eyepice and 15mm or 50mm or 75mm objectives. The Microscope, with its rack and pinion attachment is mounted on a vertical slide, which too, runs with an attached vernier along the vertical scale. The microscope is free to rotate n vertical plane. The vertical guide bar is coupled to the horizontal carriage of the microscope. for holding objects a horizontal stage made of a milki conolite sheet is provided in the base.
A Student microscope is a low power, durable optical microscope typically sold in bulk for use in school science classes. Although university science students use microscopes, the term typically refers to the type of instrument used in primary and secondary schools. For most non-scientists, the only time a microscope was ever used was in a school science class, and so when many people picture a microscope, it is a student microscope that comes to mind.
The classic school microscope, as was common in American public high schools in the second half of the 20th century, was a low power (3-10x) double lens instrument, with an eyepiece adjusted with twin knobs, one for coarse and one for fine focus adjustment. The primary lens was often mounted on a rotating platter so that different lenses could be rotated into the line of view (typically there was a choice of three different powers). The optical quality of these inexpensive microscopes was very poor, so that choosing the highest-power (and thus longest) lens was often quite useless. Due to its length, the highest-power lens often crushed the slide beneath, as the hapless student rotated the focus knob vainly trying to see something and collided with the slide, which was held in place by small metal clips. Beneath the slide was an adjustable mirror, or later, a battery powered light bulb.
A telescopic sight, commonly called a scope, is a sighting device that is based on an optical refracting telescope. They are equipped with some form of graphic image pattern (a reticle) mounted in an optically appropriate position in their optical system to give an accurate aiming point. Telescopic sights are used with all types of systems that require accurate aiming but are most commonly found on firearms, particularly rifles. Other types of sights are iron sights, reflector (reflex) sights, and laser sights.
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite (TCP/IP) to serve several billion users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic, wireless and optical networking technologies. The Internet carries an extensive range of information resources and services, such as the inter-linked hypertext documents of the World Wide Web (WWW), the infrastructure to support email, and peer-to-peer networks.
Most traditional communications media including telephone, music, film, and television are being reshaped or redefined by the Internet, giving birth to new services such as voice over Internet Protocol (VoIP) and Internet Protocol television (IPTV). Newspaper, book and other print publishing are adapting to website technology, or are reshaped into blogging and web feeds. The Internet has enabled and accelerated new forms of human interactions through instant messaging, Internet forums, and social networking. Online shopping has boomed both for major retail outlets and small artisans and traders. Business-to-business and financial services on the Internet affect supply chains across entire industries.