Category Science & Technology

How do we see distant objects with binoculars?

        If you look through binoculars, you will find distant objects appear nearer and larger. Why does this happen?

        Binoculars are a pair of small telescopes built into a frame or casting. The two telescopes in binoculars are exactly similar in structure and meant for each eye. Each telescope is built into a funnel-shaped tube or cylinder. It consists of one objective lens and one eyepiece. The objective lens is kept towards the object and the eyepiece near the eye. The lenses are anti-reflection coated. Two prisms are also mounted between the objective lens and the eye piece to make the image of the object erect.

        The light from the object falls on the objective lens and an inverted image is produced by it. This image is further inverted by the two prisms, thus the image becomes erect. The eyepiece further magnifies this image. This is how we see the erect and magnified image of the object.

      

Continue reading “How do we see distant objects with binoculars?”

What is the Theory of Relativity?

In the early nineteenth century people believed that light travelled through imaginary stationary medium called ether. It was believed that ether filled all space, and all movements could be measured absolutely with respect to it. It was also thought that the speed of light relative to a moving observer could be calculated in the same way as the relative speeds of any two moving objects. For example, just imagine two cars in the same direction: one going at a speed of 110 km/hr and the other at 80 km/hr. Passengers in the slower car would observe that the faster car is travelling at 30 km/hr.

Two American scientists, Michaelson and Morley, experimentally tried to measure the speed of earth through ether in 1887. But their result did not confirm the existence of the hypothetical medium ether. Later the explanation of negative results was offered by Albert Einstein. According to him, nothing like ether exists in the universe and the concept of absolute motion is meaningless. He also said that the speed of light is constant, no matter how fast the observer is moving. No material body can travel faster than light.

On the basis of his conclusions, Einstein formulated the Special Theory of Relativity in 1905. He showed that physical quantities like mass, length and time are also not absolute. They change as the bodies move. If a body moves with a large velocity, its mass increases and it becomes shorter. 

Continue reading “What is the Theory of Relativity?”

How is nylon made?

            Nylon is one of the most important chemical discoveries of the 20th century. It is one of the toughest, strongest and most elastic substances we have today. It is a synthetic plastic material which is made from chemicals derived from coal, water, air, petroleum, agricultural by-products and natural gas.

            It was first developed by a research team headed by a U.S. chemist Wallace H. Carothers working in E.I. Dupant de Nemours & Co. He began experimenting with it in the 1920s. In 1935, he produced the first piece of nylon. It was converted into cloth in 1937.

            Nylon is made from two chemical compounds: Hexamethylenediamine and Adipic acid. Hexamethylenediamine consists of carbon, nitrogen and hydrogen. Adipic acid contains carbon, hydrogen and oxygen. Each of these substances contains six carbon atoms and the nylon produced by them has been named as Nylon-6, 6. Manufacturers combine the two compounds to form a substance called nylon salt. A solution of nylon salt is placed in an autoclave (a heating device). The autoclave heats the solution under pressure. Water is removed and the small molecules in the compound combine to form large molecules. This process is called polymerization.

            When caprolactam is used as the starting material, Nylon -6, 6 is obtained. It has been so named because it has six carbon atoms in the basic unit. It is comparatively a recent development.

            In some factories, the newly made nylon comes out of the machines as a plastic ribbon. This is then cooled, and cut into small pieces. Nylon fibres are made by forcing molten nylon through tiny holes in a device called spinneret. The thin streams of nylon that come out of the spinneret harden into filaments when they come in contact with air. Then they are wound into bobbins. From a single bobbin, as many as 2520 filaments are united into a textile nylon yarn. The fibres are drawn or stretched after they cool. The stretching action causes molecules in the fibre to fall into straight lines and make the fibres stronger and more elastic.

            Nylon can be formed into fibres, bristles, sheets, rods, tubes and coatings. It can also he rendered into powdered form for making moulds.

            Nylon fibres resist mildew and not harmed by most kinds of oil, grease and household cleaning fluids. It absorbs little water.

            Nylon is used to make many articles of clothing, parachutes, carpets, ropes, fishing lines and upholstery. It is also used in tyres and bristles in many types of brushes. Solid pieces of nylon are used to make bearings, gears and small machine parts. Unlike metal parts nylon bearings and machine parts need little lubrication.

            Recently a nylon derivative known as Qiana has been developed. It is a silk-like fibre used in clothing. Thus nylon has proved to be useful in many ways.  

How does a crane work?

          You must have seen a crane lifting and moving heavy loads at construction sites and other places. The machine got its name from its resemblance to the crane bird which has a long neck!

          Although cranes have been in use .since ancient times, their widespread use only began in the 19th century with the development of steam engines, internal combustion engines and electric motors.

        Basically, cranes are of two types: fixed and mobile. The mobile cranes are more common. Some have a jib or boom that can move up and down and can swing around in a circle. Some others form a bridge and can lift a load up and down, move it along a track and move it from side to side above the construction site. 

          A common mobile crane is the crawler. It is mounted on a vehicle with wheels. These cranes are mainly used for civil engineering and construction work. They can lift heavy loads upto around 72 tons and can have a boom length of 30 m (100 ft) or more.

          Another type of crane is the hammer head or cantilever crane. It is used in the construction and erection of tall buildings. It has a long horizontal jib that is cantilevered and mounted on a tower. The tower can be raised by jacking it up, floor by floor, as the building becomes taller. The load is suspended from a trolley that moves along the jib. 

Continue reading “How does a crane work?”

How is an automobile’s speed measured?

          An automobile’s speed is measured by a speedometer fitted next to the steering wheel of a car. It indicates the vehicle’s speed in kilometers per hour or miles per hour. The speed is read on the dial which is numbered from 0 to 160, by means of a pointer. Most speedometers also incorporate an odometer – a device that records the distance travelled by the vehicle.

          A speedometer is driven by a flexible cable that is connected to a set of gears in the vehicle’s transmission. When the vehicle moves, the gears turn a core or flexible metal shaft inside the cable. The core turns a magnet inside a metal drum called a speed cup. This is located inside the speedometer housing. The revolving magnet exerts a turning force on the speed cup. In turn the speed cup is held back from revolving freely with the magnet, by the opposing action of a hairspring. The movement of the speed cup is transferred to the pointer on the dial. The hairspring brings the pointer back to ‘zero’ when the vehicle stops moving. Most of the speedometers register 36 km/hr when the core inside the cable revolves at 1000 revolutions per minute.

          The odometer registers total kilometers travelled by the vehicle. Some automobiles also have Trip odometers that can be reset to ‘zero’ at the beginning of a particular trip. An odometer consists of a chain of gears (with a gear ratio of 1000 : 1) that causes a drum, graduated in 10th of a mile or kilometer, to make one turn per mile or kilometer. A series, commonly of six such drums, is arranged in such a way that one of the numerals on each drum is visible in a rectangular window. The drums are coupled so that 10 revolutions of the first cause one revolution of the second and so forth, the numbers appearing in the window represent the accumulated mileage.

How is electricity conducted through wires?

Electricity is supplied to our homes, schools, factories and stores through copper or aluminium wires from power stations. These power stations burn coal or oil, use nuclear reactions or the energy of falling water to produce energy to run the generators. The power thus generated is then transmitted to different cities and places where it is required. Electricity is then transmitted through transmission lines.

To avoid the loss of power, the output voltage from the generator is first stepped up to a high voltage by a step-up transformer. After being received at the city power station, it is again reduced to low voltage, before it reaches our homes or factories. Now question arises how is electricity conducted through wires?

We know that all substances are made up of atoms. Materials which allow the passage of electricity are called conductors. Metals, such as copper, aluminium, silver and gold are good conductors of electricity. The atoms of these metals have loosely bonded electrons. These electrons are free to move within the metal. These are called free electrons and are responsible for the conduction of current. More the number of free electrons in the metal, better it conducts the electricity. 

When electric battery is connected across the ends of the metal wire, the negatively charged free electrons move away from the end connected to the negative terminals and flow toward the positive terminal. This flow of electrons is nothing but the electric current. Hence the drifting electrons cause electricity to flow. Greater the number of free electrons in a metal, easier it is for electricity to flow through it.

Some materials are poor conductors of electricity because they have less number of free electrons. Poor conductors resist the flow of electricity. The resistance of a wire depends upon its material length and area of its cross-section.

Some substances do not allow electricity to flow through them and are called insulators. These substances contain tightly-bonded electrons that cannot move away from atoms. Hence they do not conduct electricity. Glass, mica, wood, plastic and rubber are common insulators. Some substances like silicon and germanium are neither good conductors nor insulators. They are called semi-conductors.