Limitation of Sight and Hearing

Topics: Sound, Lens, Ultrasound Pages: 11 (3539 words) Published: June 16, 2013


Humans have sight and hearing limitation. Without any devices, our sight and hearing was limited. Most of the limitation of sight can be overcome with the help of certain optical instruments such as magnifying glass, microscope, binoculars and others. The range of frequency of hearing in human 20 Hz to 20 000 Hz. It was different according to the age of a person. Hearing limitations can be overcome by using devices such as microphone, stethoscope, earphone and PA system. All of these devices help us to make our live easier.


The objectives of learning about the limitation of sight :
- I have learnt that our sight and hearing has its limitation. - I have learnt we can overcome the limitation of our sight and hearing by using technology devices. The technology devices have make our life easier :

- Teachers use microphone in the assembly.
- Doctors use stethoscopes to hear our heartbeats.

Limitation of sight

Can you see the craters on the moon or a microorganism with your naked eye? How about the bones and organs inside your body? It is not possible for the eyes to see very distant objects or very tiny organisms. We also cannot see through opaque objects. These are some of the limitations of sight. Optical Illusion

An optical illusion (also called a visual illusion) is characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a perception that does not tally with a physical measurement of the stimulus source. There are three main types: literal optical illusions that create images that are different from the objects that make them, physiological ones that are the effects on the eyes and brain of excessive stimulation of a specific type (brightness, colour, size, position, tilt, movement), and cognitive illusions, the result of unconscious inferences.
A scintillating grid illusion. Shape, position, colour, and 3D contrast converge to produce the illusion of black dots at the intersections.

Blind Spot

A blind spot, scotoma, is an obscuration of the visual field. A particular blind spot known as the blindspot, or physiological blind spot, or "blind point", or punctum caecum in medical literature, is the place in the visual field that corresponds to the lack of light-detecting photoreceptor cells on the optic disc of the retina where the optic nerve passes through it. Since there are no cells to detect light on the optic disc, a part of the field of vision is not perceived. The brain interpolates the blind spot based on surrounding detail and information from the other eye, so the blind spot is not normally perceived. Although all vertebrates have this blind spot, cephalopod eyes, which are only superficially similar, do not. In them, the optic nerve approaches the receptors from behind, so it does not create a break in the retina.

Stereoscopic and monocular vision

Stereoscopic Vision
-Both eyes at the front of the head
-Both eyes are used to look at an object
-The field of stereoscopic vision is the area where the visual fields of both eyes overlap -It gives a smaller field of vision
-It forms a three-dimensional image
-Able to estimate the position and distance of an object more accurately -Human beings and predators have stereoscopic vision
-It enables predators such as owls and tigers to determine accurately the position of their prey

Monocular Vision
-An eye on each side of the head
-Only one eye is used to look at an object
-The fields of vision in both eyes either do not overlap or may overlap only a little -It gives a wider field of vision. Monocular vision sometimes covers 360 degree -It does not form a three-dimensional image

-Not able to estimate positions and distances accurately
-Prey have...
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