State the difference between:
(a) myopis and hypermetropia.
(b)tactual acids and auditory acids.
Answers
a)The eye is similar to a camera in its basic operation. There are three basic parts of the eye: a light focusing system, an automatic aperture system, and a light-sensitive detection system. Hypermetropia and Myopia, both are refractive defects in vision.
Myopia
Myopia is the term for nearsightedness. Myopia results when parallel light is focused in front of the retina. Only objects closer to the eye have a clear vision and can be properly focused on the retina. This defect is most usually linked with an elongated eyeball.
Myopia is also known as nearsightedness.
In myopia, a person is not able to see distant objects clearly.
In this defect, the lens is not able to produce a sharp image of the distant objects on the retina. Instead, the image is formed in front of the retina.
The reduction in the focal length of the eye lens is the cause behind it. Elongation of the eyeball also causes Myopia.
Myopia can be corrected by using a concave lens of suitable focal length.
Hypermetropia
Hypermetropia due to a short eyeball, causes parallel light to be focused behind the retina. This happens if the cornea does not refract the light enough. People suffering from hyperopia have blurred vision of near objects and a clear vision of farther objects.
Hypermetropia is also known as farsightedness.
A person cannot clearly see the nearby objects as the image is formed behind the retina.
The increase in focal length of the eye lens may be a cause.
It may also be caused due to flattening of the eyeball.
Hypermetropia may be corrected using the convex lens of suitable focal length.
b)Tactual aids are non-optical sensory aids which involve the use of touch, e.g. Braille system for blind people.
Auditory aids are non-optical sensory aids which involve the sense of hearing, e.g. Tape recorders, cassettes for deaf.
Explanation:
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