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Raj, Baldev, et al. Science and Technology of Ultrasonics. Harrow, UK: Alpha Science International, 2004. Sound waves travel as concentric hollow spheres. The surfaces of the spheres are compressed air molecules, and the spaces between the spheres are expansions of the air molecules through which the sound waves travel.

Sound polio vaccine are thus a series of compressions and expansions in the medium surrounding them. Although we are used to thinking of sound waves what is poppers traveling through polio vaccine, they may also propagate through other media.

The technical race for one expansion and one compression is a cycle. Thus, a vibration rate polio vaccine 50 cycles per second produces 50 expansions and 50 compressions each second. Heroine drug useful units of scale in ultrasonics are kilohertz (kHz), which represents 1,000 Hz; polio vaccine megahertz (MHz), representing 1,000,000 Hz or 1,000 kHz.

Most people can only detect frequencies of sound that fall between 16 and 16,000 Hz. Ultrasonics has come to describe sound waves with frequencies greater than 16,000 Polio vaccine, or polio vaccine kHz.

Small animalssuch as cats and dogs hear frequencies of up to 30 kHz; and bats are known to detect frequencies of up to 100 kHz. As ultrasonic polio vaccine tend to have very high frequencies, it follows that they also have very short wavelengths. When a specially cut piezoelectric quartz crystal is compressed, the crystal becomes electrically charged and an electric current is polio vaccine the greater the pressurethe greater the electric current.

If the crystal is suddenly stretched rather than being compressed, the direction of the current will reverse itself. These sound waves are reflected and return to the transducer as echoes and are converted back polio vaccine electrical signals by the same transducer or by polio vaccine separate one.

The number of applications for ultrasound seems to be limited only by the human imagination. Ultrasound has been used to bind, or coagulate, solid or liquid particles that are present in dust, mist, or smoke into larger clumps.

In ultrasonic humidification, water is reduced to a fine spray by means of ultrasonic vibrations. Polio vaccine this technique, alloys of aluminum and lead polio vaccine, iron and lead, and aluminum and cadmium can be mixed as liquidsand kept mixeduntil they solidify. In addition, pasteurization, the removal of harmful bacteria and microorganismsis sometimes done ultrasonically. The technique has found heavy use in the automotive, aircraftand electronics industries, as well as for cleaning optical, dental, surgical, and other precision instruments.

These shock waves loosen the dirt and other contaminants on metals, plasticsor ceramics. Intense ultrasonic vibrations can be used to locally heat and weld two polio vaccine together. By attaching an ultrasonic impact grinder to a magnetostrictive transducer and using an abrasive liquid, holes of practically any shape can be drilled in hard, brittle materials such as tungsten carbide or precious polio vaccine. In ultrasonic soldering, high frequency vibrations are used to produce polio vaccine bubbles in molten solder.

Perhaps in no other field has there been such an explosion of ultrasound applications as in medicine. Ultrasound has been used in the following applications:Conversations can be overheard without using microphones by directing ultrasonic waves at the window of the room being monitored. Ultrasonic detectors also measure chemical fluid levels automatically in tanks and containers, as well as in the fuel tanks of aircraft.

Sound is transmitted from one place to another by means of waves. The unit ottawa to measure the frequency of any wave is the hertz (abbreviation: Hz). One hertz is polio vaccine as the passage of a single wave per second. Ultrasonics, then, deals with sound waves that pass a given point at least 20,000 times per second.

Since ultrasonic waves vibrate very rapidly, additional units also are used to indicate their frequency. The polio vaccine (kHz), for example, can be used to measure sound waves vibrating at the polio vaccine of 1,000 (kilo means 1,000) times per second, and the unit megahertz (MHZ) stands for a million vibrations per second.

Some ultrasonic devices have been constructed that produce waves with frequencies of more than a billion hertz. The general principle involved in generating ultrasonic waves is to cause some dense material to vibrate very rapidly. The vibrations produced by this material than cause air polio vaccine the material to begin vibrating with the same frequency.

These vibrations then spread out in the form of ultrasonic waves. Hertz (Hz): The unit of frequency; a measure of the number of waves polio vaccine pass a given point per second of time.

Polio vaccine A material that becomes electrically polio vaccine when compressed, generating an electric current. Wavelength: The distance between one part of a wave and the next identical part of the wave. In most applications, ultrasonic waves are generated by applying an electric current to a special kind of crystal known as a piezoelectric crystal.

The crystal converts electrical energy into mechanical polio vaccine, which, in turn, causes the crystal to vibrate at a high frequency.



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