Difference Between Radar and Sonar

Radar vs Sonar
RADAR and SONAR are both detection systems used to identify objects and their position related parameters when they are at a distance and not directly observable. RADAR stands for RAdio Detection and Ranging, and SONAR stands for SOund Navigation And Ranging. Both detection systems use the method for detection of the reflection of a transmitted signal. The type of the signal used in the system makes all the difference; RADAR uses radio waves, which are electromagnetic waves and SONAR uses acoustic or sound waves, which are mechanical waves.

How Radar Works
Radar sets, also called radar systems, come in many different sizes, depending on the job they are expected to do. But all have four main parts — a transmitter, an antenna, a receiver, and an indicator (display screen). The transmitter produces the radio waves. When a radio wave strikes an object such as an airplane, part of the wave is reflected back to the radar set. The signal is detected by the antenna as a radio echo. The returning echo is sent to the receiver, where its strength is increased, or amplified. The echo is usually displayed as an image that can be seen on the indicator.
A common type of radar is called pulse radar. This type of radar sends out radio waves in short bursts, or pulses. The distance to a target is determined by the time it takes the signal to reach the target and the echo to return. Radio signals travel at a known speed — about 186,000 miles (300,000 kilometers) per second, the speed of light. If the radio signal comes back in 1/1,000 second, then the round trip is 186 miles (300 kilometers). The target must be half that far, or 93 miles (150 kilometers) away.
Pulsed transmission helps determine the distance more accurately. Why is this so? Imagine that you are about to shout across a canyon to make an echo. If you shout a long sentence, the first words will come back before you can finish. It would be impossible to hear the entire echo clearly because it would be mixed with your own speech. But if you shout a short word the echo comes back crisp and clear with no interference from the transmitter (you).

How Sonar Works
There are two types of sonar sets: active and passive. An active sonar set sends out sound pulses called pings, then receives the returning sound echo. Passive sonar sets receive sound echoes without transmitting their own sound signals.In active sonar sets, the sound signals are very powerful compared with ordinary sounds. Most sonar sets send out sounds that are millions of times more powerful than a shout. Each ping lasts a fraction of a second.
Some sonar sets emit sounds you can hear. Other sonar signals are pitched so high that the human ear cannot hear them. These signals are called ultrasonic waves. (“Ultra” means “beyond,” and “sonic” means “sound.”) The sonar set has a special receiver that can pick up the returning echoes. The location of underwater objects can then be determined by the length of time that elapses between sending the signal and hearing the returning echo.