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Discussion : importance of safety equipment

Working in groups of 5, discuss the importance of safety equipment such as ear protectors for workers in loud environments, e.g. those who use jack hammers or direct aeroplanes to their parking bays. Write up your conclusions in a one page report. Some prior research into the importance of safety equipment might be necessary to complete this group discussion.

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Ultrasound is sound with a frequency that is higher than 20 kHz. Some animals, such as dogs, dolphins, and bats, have an upper limit that is greater than that of the human ear and can hear ultrasound.

The most common use of ultrasound is to create images, and has industrial and medical applications. The use of ultrasound to create images is based on the reflection and transmission of a wave at a boundary. When an ultrasound wave travels inside an object that is made up of different materials such as the human body, each time it encounters a boundary, e.g. between bone and muscle, or muscle and fat, part of the wave is reflected and part of it is transmitted. The reflected rays are detected and used to construct an image of the object.

Ultrasound in medicine can visualise muscle and soft tissue, making them useful for scanning the organs, and is commonly used during pregnancy. Ultrasound is a safe, non-invasive method of looking inside the human body.

Ultrasound sources may be used to generate local heating in biological tissue, with applications in physical therapy and cancer treatment. Focussed ultrasound sources may be used to break up kidney stones.

Ultrasonic cleaners, sometimes called supersonic cleaners, are used at frequencies from 20-40 kHz for jewellery, lenses and other optical parts, watches, dental instruments, surgical instruments and industrial parts. These cleaners consist of containers with a fluid in which the object to be cleaned is placed. Ultrasonic waves are then sent into the fluid. The main mechanism for cleaning action in an ultrasonic cleaner is actually the energy released from the collapse of millions of microscopic bubbles occurring in the liquid of the cleaner.

Interesting fact

Ultrasound generator/speaker systems are sold with claims that they frighten away rodents and insects, but there is no scientific evidence that the devices work; controlled tests have shown that rodents quickly learn that the speakers are harmless.

In echo-sounding the reflections from ultrasound pulses that are bounced off objects (for example the bottom of the sea, fish etc.) are picked up. The reflections are timed and since their speed is known, the distance to the object can be found. This information can be built into a picture of the object that reflects the ultrasound pulses.


Ships on the ocean make use of the reflecting properties of sound waves to determine the depth of the ocean. A sound wave is transmitted and bounces off the seabed. Because the speed of sound is known and the time lapse between sending and receiving the sound can be measured, the distance from the ship to the bottom of the ocean can be determined, This is called sonar, which stands from So und N avigation A nd R anging.

Questions & Answers

Which can involve the London dispersion forces a. CF4 b. HCL c. H2O d. MgO
Pinky Reply
how do I calculate the angle of refraction
Sibusiso Reply
use Snell's law
what diference vector ans scalar
Khayalethu Reply
what is newtons first law basically about?
Think about it like this: Okay so you're in a car right and it's going straight right? The car then suddenly takes a sharp right turn, have you noticed that your body resists going to the right, so it kinda goes in the opposite direction /the direction the car was originally going in.
This is called inertia so your body is resisting the change in its motion.
So basically newton's first law states that and object will CONTINUE in its state of rest/uniform velocity in a straight line unless it is acted upon by a resultant force.
it resist the change occuring in the body.
how do you calculate the angle of incidence ?
Thabisa Reply
what happen when a ray light of energy is converted into another form of energy
Hansromy Reply
how do you run the demo?
Lauren Reply
what is a covalent bond
Mbuso Reply
a bond in which two orbitals overlap and share an electron
sorry I made a mistake i meant to say that it is a bond in which 2 orbitals overlap and the atoms share an electron pair
Is this notes are for chemistry?
what angle does atoms bond at when it is a trigonal planar shape
Olebogeng Reply
what is the graph of acceleration vs force?
Kgothatso Reply
investigate the relationship between force and acceleration
Hlumelo Reply
Aim : investigate the relationship between force and acceleration
The relationship between force and direction is directly proportional, which means that when force increases acceleration increases and if it decreases so does acceleration
Law of Acceleration - The acceleration of an object is directly proportional to the force acting on it and inversely proportional to the mass of the object.
how to calculate frictional force
Esesethu Reply
frictional force =to the parallel component of weight Fgsin
What are the effects of Intermolecular forces
Mpho Reply
Solid, liquid and gas
what is meant by the term induced momentary dipole
Lucky Reply
induced means forced so in this type of a intermolecular force a dipole is forced
What is the difference between acceleration and force
Fanini Reply
what is the definition of bond length
Mmabophelo Reply
Bond length is the average distance between the nuclei of 2 bonded atoms

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Source:  OpenStax, Siyavula textbooks: grade 11 physical science. OpenStax CNX. Jul 29, 2011 Download for free at http://cnx.org/content/col11241/1.2
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