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प्रश्न
Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.
- Is she short-sighted or long-sighted?
- What type of lenses-converging or diverging-would an optician prescribe for her?
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उत्तर
- She is short-sighted.
- An optician would prescribe diverging lenses to correct her defect.
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संबंधित प्रश्न
In a Std. X class out of 40 students 10 students use spectacles, 2 students have positive power and 8 students have negative power of lenses in their spectacles.
Answer the following questions:
(1) What does the negative power indicate?
(2) What does the positive power indicate?
(3) Generally which type of spectacles do most of the students use?
(4) What defect of eyesight do most of the students suffer from?
(5) Give two possible reasons for the above defect.
What is myopia?
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
A student is unable to see clearly the words written on the black board placed at a distance of approximately 3 m from him. Name the defect of vision the boy is suffering from. State the possible causes of this defect and explain the method of correcting it.
What is the other name of old age hypermetropia?
A man can read the number of a distant bus clearly but he finds difficulty in reading a book.
- From which defect of the eye is he suffering?
- What type of spectacle lens should he use to correct the defect?
What is short-sightedness? State the two causes of short-sightedness (or myopia). With the help of ray diagrams, show:
(i) the eye-defect short-sightedness.
(ii) correction of short-sightedness by using a lens.
Name the following:
The photosensitive pigment present in the rods of the retina.
What is meant by optical illusion? Give one example.
A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?
The diagram alongside represents a section of a mammalian eye.
(i) Label the parts 1 to 5 of the diagram.
(ii) State the function of the parts labelled 4 and 5.
(iii) With the help of a diagram show the short sightedness.
Given below is a diagram depicting a defect of the human eye? Study the same and answer the question that follow:
Name the parts labeled 1 to 4.
What type of lens is used to correct Astigmatism?
Complete the following sentence with appropriate word :
An inability to focus on nearby objects due to loss of elasticity of the lens with age is called Iris.
Due to elongation of _______ and increase in curvature of the eye lens, a person cannot see distant objects clearly.
Nearsightedness: elongated eyeball : : farsightedness: _______
A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power:
