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Question
You do not enjoy watching a movie from a very short distance from the screen in a cinema hall. Why?
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Solution
Our eyes are designed to focus at a great variety of distances. To focus constantly at a short distance can make the lens focusing muscles fatigued. Therefore, we do not enjoy watching a movie from a very short distance from the screen in cinema hall.
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About 45 lac people in the developing countries are suffering from corneal blindness. About 30 lac children below the age of 12 years suffering from this defect can be cured by replacing the defective cornea with the cornea of a donated eye. How and why can students of your age involve themselves to create awareness about this fact among people?
What is the scientific name of
long-sightedness?
The defect of vision in which the eye-lens of a person gets progressively cloudy resulting in blurred vision is called:
(a) myopia
(b) presbyopia
(c) colourblindness
(d) cataract
Name the following:
The eye defect caused due to shortening of the eye ball from front to back.
What is meant by optical illusion? Give one example.
Describe the mechanism of focusing the image of a distant object in your eye when you raise your head after reading a book.
Distinguish between the following pair of words:
Myopia and hypermetropia
Differentiate between:
Myopia and Hypermetropia.
With respect to human eye explain:
(i) How is the image formed on the retina?
(ii) How is the amount of light entering the eye-controlled?
(iii) What type of lens is used for the correction of ‘Long sight’ defect?
(iv) With the help of a ray, diagram show the defect of the eye and then its correction after the use of a lens.
Observe the following diagram and answer questions following it:
- Identify the defect of vision shown.
- List its two causes.
- Name the type of lens used for the correction of this defect.
