R A D A R

A motorist in a hurry steps on the gas and exceeds the speed limit. As the car goes over a hill, a police officer steps from the shoulder of the road and flags down in the car. The officer tells the driver; you were going 45 miles an hour in a 25 miles an hour zone. The motorist groans, oh no, it had to be radar. Police officers do catch speeding motorists with the help of radar.

WORKING:

RADAR uses short waves called i to see thing not visible to the human eye. When microwaves strike an object, they bounce off. Some of them return to their source, just as a sound echo does. By studying the returning microwaves, people can find out the size and the location of objects hundreds or even thousands miles away.

UNITS:

Microwaves vibrate just as sound and radio waves do. When microwave bounce off a moving object, they vibrate differently when they return. If the object is moving away, the returning waves vibrate differently when they return. If the object is moving away, the returning waves vibrate more slowly. If the object is approaching, the returning waves vibrate more quickly. Radar guns measure the difference between the outgoing and the incoming vibrations. Then they translate the information into a number that tells how fast the object is moving.

Radar units come in many sizes and shapes. The radar gun used to detect speeding motorists fit in the hand. Other units are as large as buildings.

USES:

At the base ball game or in cricket, a New York Mets hurls a ball towards a catcher ( in cricket bowler bowl to batsmen). A radar gun records the speed of the ball in miles an hour. Many professional baseball teams now use radar to measure how fast their pitchers ( in cricket bowlers) throw (bowls) the ball. This information helps a coach determine when a pitcher is tiring. Team scouts looking for new talent use radar to rest the pitching strength of young players. Radar also helps in measuring speeds in car, boat, sky racing.

Microwave from radar gun bounces back from moving car. The returning waves differ from the outgoing ones. That is because the waves vibrate faster after they bounce off the car. If the car were heading away, from the gun, the returning waves would vibrate more slowly Sound,radio and light waves also change when they bounce off moving objects. You can hear sound waves change. Ask an adult to drive a car past you while blowing the horn. The horn will have high pitch as the car nears you. After it passes, the horn will sound lower.