Current Affairs 8th Class

Category : 8th Class

       Introduction

Light is a form of energy, which produces the sensation of vision. The sense ofsight is one of the important senses that the God has given to the humanbeings. The object, such as, the Sun, the stars, lamps, even lightning bugs,gives off light. They are called luminous bodies (from the Latin word lumen,meaning light). Other objects, such as, trees, grass, keyboard etc. are theexamples of non luminous objects. They are visible only when they receivelight from some luminous sources and reflect it to our eyes.

Whether a body is luminous or non luminous, depends much on the nature ofmaterial of which it is made up of. By changing the nature of material, we canmake many familiar objects, both luminous ornon luminous, at will. Thefilament, or fine wire inside an electric light bulb is non luminous, unless it isheated by an electric current passing through it. We can take a piece of ironand make it glow red, yellow, or white by heating it in burning coals or over agas flame. When solid and liquid, such as, melted metals are heated totemperatures above 800 degrees Celsius (about 1500 degrees Fahrenheit), theyturn to be a source of light. Such materials are called incandescent bodies. Wecan, in fact, see any object only when ray of light falls on it and gets reflected..