What is a LensA lens is a curved and polished piece of glass or any other transparent material. The most common place where you will find lenses is in spectacles. You will also find lenses in magnifying glasses, binoculars, and in cameras. Fig. Lenses us…

Who discovered the magnet?According to a legend, the first magnet was discovered by a Greek shepherd named Magnes. It is said that the nails in his shoes and the iron tip of his staff got stuck to a large black rock on which he was standing. Greeks name…

How is Colour FormedTake a CD (compact disc) out in the sun and see how light is reflected from its shining surface. What do you see? Many colours. These colours actually come from the sunlight.White light is composed of many colours. When these colours …

What is Newton’s DiscNewton’s disc is a coloured disc which is painted with the colours of white light [i.e., violet, indigo, blue, green, yellow, orange, and red (VIBGYOR)] in equal proportions so that when it is rotated very fast, the disc appears whit…

How does an electric bell work using electromagnets?Electromagnets have a wide range of uses in all sorts of devices. Can you think of some devices from everyday life where we use electromagnets? Electromagnets are used in cranes to pick up cars in scra…

What is SpeedWhen we say a body moves fast (or slow) we refer to its speed.The speed of an object is defined as the distance travelled by it in unit time. .The SI unit of speed is metre per second (m/s).Therefore, an object that moves faster covers more…

How many Objects are there in Our Solar SystemSolar SystemThe sun and everything that revolves around it form the solar system. The planets and their moons, comets, asteroids, and other space objects orbit the sun. All these objects are held together in…

How did the Star Constellations Get their NamesConstellationsMany a times certain groups of stars seem to form a recognizable pattern in the night sky. These are called constellations. These were named by the ancient people after animals and mythological…

Where are the Stars FoundStarsStars are luminous bodies (i.e., bodies that give light) regularly seen as points of light in the night sky. Our sun is a star too. Many of the stars that we see are much bigger than the sun. Since they are very far away fro…

How can We Protect Ourselves from an EarthquakeProtection Against EarthquakesIt is not in our power to prevent an earthquake. We can, however, take precautions to minimize the damage caused by it.Since most damage to human life is caused by falling of b…