Millions fly daily in aircraft to travel across thousands of kilometers. A pilot cannot fly a plane by sight alone. In adverse conditions, such as flying at night and in a dense fog of winter, he needs the assistance of a device called radar. It is an alternative way of navigating. Human eyes have limitations regarding speed as well and cannot judge the speed of objects moving at speed towards a plane. Radar can be useful in these cases. It helps a pilot to show how fast nearby planes or birds are flying.

When a stone is thrown into water it produces oscillations, i.e. the water moves down and then returns towards its original position. However, as it returns it gathers speed and overshoots the equilibrium level. The oscillations continue for some time and the disturbance is propagated outwards as circles of ever-increasing diameter. As they travel outwards from the source the waves carry energy. The waves can be reflected by structures or boundaries; they can be refracted if they are slowed down (for example by going into shallower water); they can be diffracted around objects such as rocks or piers.

In the early 1800s, radio waves were shown to have these same properties and so it was considered to be some kind of wave. In 1832 Michael Faraday had already come to the conclusion that light was some kind of electromagnetic wave although it took him over ten years to get the evidence he had been looking for.

A radar sends the radio waves towards the articles moving. These waves come back as an echo and give information about the object. Radar is of critical importance for controlling the air traffic, moving planes safely in the air so that they do not crash with each other. The utility of radar is not limited to air movements only. It is quite helpful in predicting storms and wind speeds. In this way, it saves human lives.

In wars, radar is of special use. It is used in finding enemy aircraft and controlling air-to-air missiles, rockets, and guns. It is used in bombers to find surface targets, fixed or moving, and to navigate and avoid obstacles. The first radar was developed for use in the First World War in the 1930s. Later, it became part of air vehicle control systems. It has now become an inherent part of our safe air travel.