My Science School

          Whatever we hear with our ears is called ‘sound’. In scientific terms, sound is a kind of disturbance which produces sensations in the ears. Like heat and light, sound is also a form of energy. Do know how sound is produced and how it travels from one place to another?

          A body produces sound when a part or the whole of it vibrates. When we strike a bell, vibrations are produced in it that create sound: If we touch a ringing bell with our hands, we can easily feel the vibrations in it. Whenever a living being speaks, the diaphragm in his throat vibrates. Sound can never be produced without vibrations.

         Whenever a body vibrates, sound waves emanate from it and travel in a medium. When these waves reach our ears we hear the sound. Our ears are sensitive to sounds which are produced by vibrations of frequencies ranging between 20 to 20,000 hertz. Human ears cannot perceive frequencies of less than 20 hertz and more than 20,000 hertz.

          Sound travels from one place to another in the form of waves which need a material medium. They cannot travel in vacuum. This can be proved by a simple experiment.

          Take a glass bottle without bottom and connect it to a vacuum pump. Put a cork on its mouth. Suspend an electric bell inside this bottle. Connect the bell to a battery. It starts ringing and we hear the sound very clearly. Now start evacuating the air from the bottle with the help of the vacuum pump. As the amount of air in the bottle starts decreasing, the intensity of sound also decreases proportionately. When all the air is sucked out of the bottle we do not hear any sound. This experiment proves that a medium is always necessary for the propagation of sound waves.

          The aforesaid facts lead to three conclusions. First, sound is produced by vibrations. Second, sound travels in the form of waves. And third, sound needs a material medium for its propagation. Sound can travel through gases, liquids and solids. It travels fastest in solids, followed by liquids and slowest in gases. It cannot travel in space because there is no material medium present there. That is why astronauts talk to each other with the help of radio sets.

 

          Weather is the day to day changes in the state of the earth’s atmosphere. Everyday, we get weather forecast through newspaper, radio and television. The weather experts predict about the possibility of rain, storm or thunder showers. Do you know how this information is obtained? 

          Scientists have to study many aspects to make predictions about the weather. In fact, weather forecasting is the practical application of the knowledge gained through the study of weather behaviour, termed as meteorology. The weather depends mainly on atmosphere i.e. pressure, wind direction, humidity, ambient temperature, cloud formation, rains, snowfall etc. Weather forecasting is organized nationally by government agencies and is coordinated internationally by the “World Meteorological Organization” (WMO). There are three basic stages; observation, analysis and forecasting. Observation involves round-the-clock weather watching and gathering of meteorological data by land stations, balloon launching and also by using satellites. In analysis, information is coordinated at national centres and plotted in terms of weather maps and charts. Then in forecasting, predictions of future weather pattern are made by the “synoptic method” – in which the forecaster applies his experience of evaluation of the past weather patterns to current situation. Computers at these centres analyze the data collected by different methods. Now a day the use of supercomputers have revolutionized the area of forecasting.

          An instrument named ‘anemometer’ is used to measure the speed and the direction of the wind, whereas another kind of instrument called ‘hygrometer’ is used to measure the humidity present in the air. Rain gauges measure the amount of rainfall, while sunshine recorders measure the duration of the sunshine. ‘Maximum-minimum thermometers’ give information about varying temperatures during the twenty-four hours of a day. The atmospheric pressure is measured with the help of barometers.

          Sudden drop in the atmospheric pressure indicates the possibility of a storm or hurricane. Gradual drop in the pressure indicates the increase in the humidity and as such the possibility of rain. Easterly winds are also indicators of rain. Rise in the atmospheric pressure heralds fine weather.

          Radio waves belong to the family of electromagnetic waves which owe their existence to moving electrons. The existence of radiowaves was first predicted by James Clerk Maxwell in 1860, but it was not until 1887 that Heinrich Hertz succeeded in producing them experimentally. “Wireless” telegraphy was first demonstrated by Sir Oliver Lodge in 1894 and it was Guglielmo Marconi, the Italian scientist, who could first successfully transmit a long distance transmission in 1900 with the help of radiowaves.

          It is through radio waves only that sound from the broadcasting station is able to reach our radios. Their use is also made to transmit a variety of programmes. Radio waves work as the carriers for communication signals. The message is modulated with radio waves and transmitted with the help of a transmitter. The modulated signal is received by the radio receiver and then decoded. Radio waves were also used to keep in contact with the flying planes. With the help of these waves they are properly guided and controlled during flights thus avoiding accidents.

          Radio waves are in fact invisible electromagnetic waves which travel with the speed of light, i.e. at 300,000 km. per second. Satellites and spacecrafts keep in contact with the earth stations with the help of these waves. Live communication with the satellites and astronauts has become possible only due to radio waves. These waves can travel both through the air and the vacuum. They can even travel in water and underground to a distance of a few metres. Communication is established between the ships with the help of these waves. Every ship is equipped with radio transmitters and receivers.

          To study the radio waves originating from the different heavenly bodies, scientists make use of radio telescopes. With the help of these telescopes, it has now become possible to identify the planets and stars which generate the radio waves.

          Radio waves are also used by police. They have the equipments by which they can send and receive messages from moving vehicles. Fire brigades also use of radio waves while providing help in accidents. These waves are also used to control traffic. Today we have the instruments which can measure the speed of a moving vehicle from the control room itself.

          In a nutshell, we can say that the world has shrunk due to these radio waves.