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Devices Used To Overcome The Limitation Of Sight And Hearing (HALF-DONE)
Transcript of Devices Used To Overcome The Limitation Of Sight And Hearing (HALF-DONE)
Teacher: Pn Siti Khatijah bt Mokhtar Devices Used To Overcome
The Limitations Of Sight And Hearing Limitations Of Sight INFORMATION a) Ultrasound
Scanning Device b) X-ray Machine B6D1E1 Introduction According to the Oxford Dictionary:
A limiting rule or circumstance; a restriction:
a) A condition of limited ability; a defect or failing
b) The action of limiting something
the faculty or power of seeing:
a) the action or fact of seeing someone or something
b) the area or distance within which someone can see or something can be seen
c) dated a person’s view or consideration
the faculty of perceiving sounds:
a) the range within which sounds may be heard; earshot
We, as humans have many defects and limitations. These limitations include the physical limitations, mental limitations, sight limitations, hearing limitations and many more. These limits can be overcome by various devices invented by us humans over the years. Objectives Through this scrapbook, we will explore into the limitations of sight and hearing and the devices used to overcome these defects. The main objective of this scrapbook include:
To have a greater knowledge about the devices invented to overcome the limitations of hearing and sight.
To understand and appreciate the devices invented to overcome the limitations of sight and hearing.
•To share with the reader’s a brief information on the limitations of sight and hearing. 1. Blind spot
At certain distance from the eye, some object that you can see previously may disappear, after certain moment, it will reappear. This phenomenon occurs because the image of the object has fallen onto the blind spot in your eye. This blind spot does not have any photoreceptors. As result, the image of the cross that falls on this spot cannot be detected, and that's why you can't see it.
2. Optical illusion
Optical illusions are caused by disturbances to the nerve impulses going to the brain. The disturbances may cause by the object or condition around the object. The brain cannot accurately interpret the information sent by the receptors in eye. That’s why you will incorrectly interpret what you actually see.
These limitations can be ovecomed by the following devices. Ultrasound is an oscillating sound pressure wave with a frequency greater than the upper limit of the human hearing range. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz. Function: i. A common use of ultrasound is in underwater range finding called Sonar. An ultrasonic pulse is generated in a particular direction. If there is an object in the path of this pulse, part or all of the pulse will be reflected back to the transmitter as an echo and can be detected through the receiver path. It is possible to determine the distance. ii. Diagnostic ultrasound is used externally in horses for evaluation of soft tissue and tendon injuries, and internally in particular for reproductive work – evaluation of the reproductive tract of the mare and pregnancy detection Acoustics, the science of sound, starts as far back as Pythagoras in the 6th century BC, who wrote on the mathematical properties of stringed instruments. Sir Francis Galton constructed a whistle producing ultrasound in 1893. The first technological application of ultrasound was an attempt to detect icebergs by Paul Langevin in 1917. The piezoelectric effect, discovered by Jacques and Pierre Curie in 1880, was useful in transducers to generate and detect ultrasonic waves in air and water. History Pythagoras wrote the mathematical
properties of stringed instruments. Francis Galton constructed a
whistle producing ultrasound
in 1893 The first technological application of ultrasound was an attempt to detect icebergs by Paul Langevin in 1917 An ultrasonic examination
in East Germany, 1990 Hermann von Helmholtz formulated mathematical equations for X-rays. Physicist Johann Hittorf observed tubes with energy rays extending from a negative electrode. William Crookes investigated the effects of energy discharges on rare gases. Heinrich Hertz began experimenting and demonstrated that cathode rays could penetrate very thin metal foil (such as aluminium). In 1887, Nikola Tesla began to investigate X-rays and produced the bremsstrahlung process. In 1895, Wilhelm Röntgen began observing and further documenting X-rays while experimenting with vacuum tubes. On January 18, 1896 an X-ray machine was formally displayed by H.L. Smith.
One of the first X-ray photographs was made of the hand of Röntgen's wife. The image displayed both her wedding ring and bones.
In the 1940s and 1950s, X-ray machines were used in stores to help sell footwear. These were known as fluoroscopes. However, as the harmful effects of X-ray radiation were properly considered, they finally fell out of use. Shoe-fitting use of the device was first banned by the state of Pennsylvania in 1957. (They were more a clever marketing tool to attract customers, rather than a fitting aid. History Function X-rays are like light in that they are electromagnetic waves, but they are more energetic so they can penetrate many materials to varying degrees. When the X-rays hit the film, they expose it just as light would. Since bone, fat, muscle, tumors and other masses all absorb X-rays at different levels, the image on the film lets you see different (distinct) structures inside the body because of the different levels of exposure on the film.