SCIENCE CAPSULES

Land line :      Here, microphone converts voice into electrical signals, amplified and is sent through wire.  At the other end, electrical variations are converted into sound by the speaker.  Today electrical signals are converted into laser signals and sent through glass fibers.  We know land line is the two way communication (send and receive).    Radio :  Here, electrical signals are superimposed on high frequency radio waves.  Then the radio waves are radiated from tower.  High frequency waves has high energy and they can travel to long distance.  When you put a powerful light on the top of a tower, it will spread to long distance.  Similarly, high wattage radio waves (invisible light) spread to wide area. Wireless communication had begun .  Voice only is sent over the radio.  It is a one way communication, receiving only.  At the receiving end signals are extracted from radio waves and fed to...

    When a child reads a book, he adds letter by letter and form words; collects words together and make a sentence; goes through sentence by sentence and completes a page.  Similarly, a picture is scanned in computer, TV, etc.,      A picture is divided into number of lines and each line is split up into number of points.  A point is called a pixel(picture element).  Hence the picture is read pixel by pixel and line by line.      Each pixel has brightness info and colour info. Each pixel's info is converted into electrical signal(voltage) then into digital form(0s and 1s).  When the whole picture is converted into electrical form or digital form, it can be stored, manipulated and transmitted using high frequency waves.             Scanning occurs in TV, camera, Computers, CAT scan , photocopier etc,. Note:  In TV. 625 lines are scanned in one picture and 25 pictures are transmi...