Physics seminar

The topic of our seminar is :the sound

A . Range of hearing

B . Uses of ultrasound

Range of hearingRange of hearing

The audible range of human being to hear is from 20 Hz to 20000 Hz .children under the age of five and

some animals can hear up to 25 kHz

Older people cannot hear properly

And range below 20 Hz are called infra sonic sound

Rhinos communicate using 5 Hz of noise

Frequencies higher than 25 kHz is called ultra sonic sound

Application of ultra sound

Ultrasonic cleaning

 Ultrasonic cleaners, sometimes mistakenly called supersonic cleaners, are used at frequencies from 20 to 40 kHz for jewelry, lenses and other optical parts, watches, dental instruments, surgical instruments, diving regulators and industrial parts.

An ultrasonic cleaner works mostly by energy released from the collapse of millions of microscopic cavitation's near the dirty surface.

The bubbles made by cavitation collapse forming tiny jets directed at the surface.

Ultrasonic disintegration

Similar to ultrasonic cleaning, biological cells including bacteria can be disintegrated. High power ultrasound produces cavitation that facilitates particle disintegration or reactions.

This has uses in biological science for analytical or chemical purposes (sonication and sonoporation) and in killing bacteria in sewage.

High power ultrasound can disintegrate corn slurry and enhance liquefaction and saccharification for higher ethanol yield in dry corn milling plants.

Ultrasonic humidifier

The ultrasonic humidifier, one type of nebulizer (a device that creates a very fine spray), is a popular type of humidifier. It works by vibrating a metal plate at ultrasonic frequencies to nebulize (sometimes incorrectly called "atomize") the water. Because the water is not heated for evaporation, it produces a cool mist. The ultrasonic pressure waves nebulize not only the water but also materials in the water including calcium, other minerals, viruses, fungi, bacteria, and other impurities. Illness caused by impurities that reside in a humidifier's reservoir fall under the heading of "Humidifier Fever".

Ultrasonic humidifiers are frequently used in aeroponics, where they are generally referred to as foggers.

Ultra sonic welding

In ultrasonic welding of plastics, high frequency (15 kHz to 40 kHz ) low amplitude vibration is used to create heat by way of friction between the materials to be joined.

The interface of the two parts is specially designed to concentrate the energy for the maximum weld strength.

It can be used to detect

flaws in the objects such as buildings ,blocks,iron and etc

It is used in medicine for many purposes

A

The destroying of kidney stones

B

They can destroy cataract

C

We can see the baby inside mothers womb .without x- ray using ultra sonic waves which wont affect the fetus

The end