1. P HYSICS P ROJECT Group member: Essa Salem Rashed Khalil Abdulaziz Jamel

2. U LTRASONIC WAVES Ultrasonic waves:- Are sound waves of extremely high frequency (over 20 000 Hz) indiscernible for a healthy young adult’s ear. As you grow the frequency that you can hear becomes higher and higher.

3. U SES is used for examining different body structures, performed in much the same way as X-ray. Used in ships to detect icebergs. Used by bats to detect the location of their food. Used in cars to detect obstacles. Ultrasound is also used by dolphins and whales to detect obstacles and for communication.

4. How Sonar Works Under Water In the 19th century an underwater bell was used as an ancillary to lighthouses to provide warning of hazards. The use of sound to echo locate underwater in the same way as bats use sound for aerial navigation. The world's first patent for an underwater echo ranging device was filed at the British Patent Office by English meteorologist Lewis Richardson a month after the sinking of the Titanic, and a German physicist called Alexander Behm obtained a patent for an echo sounder in 1913. Sonar, which stands for sound navigation and ranging, is a technique that uses sound propagation to navigate, communicate with or detect other vessels. There are 2 technologies of sonar:

5. Passive sonar: passive sonar is essentially listening for the sound made by vess els. Active sonar: active sonar is emitting pulses of sounds and listening for echoes. The sound reflection characteristics of the target of an active sonar, such as a subm arine, are known as its target strength. A complication is that echoes are also obtained from other objects in the sea such as whales for example.

6. L INKS Ultrasonic waves: http://www.youtube.com/watch?v=Q_5qcqDN1cU Uses: http://www.youtube.com/watch?v=gZxLUNHEmPw &feature=related http://www.youtube.com/watch?v=B2teeVAnnRM Videos http://www.youtube.com/watch?v=voL0qDbjfSg http://www.youtube.com/watch?v=Yjz5bcKoogg