## Calculating distance of submarine and aero plane

Calculating distance of submarine and aero plane in sky can be made by two following ways.

Distance of submerged objects or submarines in sea (Sound Navigation and Ranging- SONAR)

SONAR  is an instrument which uses ultrasonic waves (waves having frequency > 20, 000 Hertz) to detect and locate the submerged objects, submarines etc. in sea. Ultrasonic waves produced from a transmitter are sent towards the distant object under water. When the object comes in the direction of ultrasonic waves, then the waves are reflected back from it. Measuring the time interval t between the instant the ultrasonic waves are sent and received back, the distance s of the object can be calculated by the relation.
s= ct/2
Where c is the velocity of ultrasonic waves

### Distance of aero plane in the sky (Radio Detecting and Ranging-RADAR)

RADAR is an instrument which uses radio waves for detecting and locating an aero pane. Radio waves produced by a transmitter at the radar station, are sent towards the aero plane in space. These waves are reflected from the aeroplane . The reflected waves are received by a receiver at the radar station. Nothing the time interval between the instant of transmission of waves and their direction, distance of aeroplane can be measured. If t is the required time interval and c is the velocity of light (=equal to the velocity of radio waves) then distance of aeroplane.
s= c×t/2