The word ‘radar’ is an acronym for ‘radio detection and ranging’. It is, in fact, an electronic device by which one can detect and measure an invisible flying object’s distance and speed. It can work efficiently under all weather conditions such as fog, mist, smoke, snowfall, storm, cyclone, rains, etc. It is due to these reasons that radar is used in the traffic control room of airports for the guidance of airplanes. It also helps to guide ships. The radar works on the principle of ‘echo’, much like sonar. The sound waves reflected by some obstacle produce an echo. Similarly, radio waves, which are electromagnetic in nature, also get reflected when they encounter some obstacle in their path. Scientists discovered this property of radio waves in 1930. Using this property, in 1935, five radar centres were established in America. Major developments in the field of radars took place during the Second World War. They were of great help in detecting enemy bombers. Since then, many kinds of radars have been developed for peaceful uses also. Now, there are radars installed even in fighter aircraft. Radars help in controlling and guiding the path of unmanned spacecrafts. They are also used in giving information related to weather. Have you ever wondered how it works? Radars make use of radio waves. These waves are similar to those used in radio broadcasting. However, the radio waves used in radar have higher frequencies. These waves are called microwaves. The speed of these waves is equal to that of light, i.e., 3×108 metres (186,000 miles) per second. Each radar centre has a transmitter, which sends out radio waves with the help of an antenna towards an object. It also has a receiver, which receives the radio waves reflected by the object. The receiver has a screen that shows the object’s position in the sky. The time taken by the radio waves in sending from the transmitter to the object and returning to the receiver is recorded by radar. By multiplying this time with the velocity of light, we get twice the distance between the radar and the object. This is how the distance of an object is found with the help of radar. The radar has automatic instruments that perform all these calculations. Initially, radars were very big in size, but today they can fit in our palms.