Advertisements
Advertisements
प्रश्न
Write scientific reason.
Nearsightedness, this defect can be corrected by using spectacles with concave lens.
Advertisements
उत्तर
- Nearsightedness arises due to slight elongation of the eyeball causing an increase in the distance between the eye lens and the retina or due to an increase in the curvature of the cornea and eye lens resulting in increased converging power.
- As a result, light from a distant object arriving at the eye-lens gets converged at a point in front of the retina.
- When a concave lens of suitable focal length is placed between the eye and object, due to the diverging effect of the concave lens, the image gets focussed on the retina.
Thus, nearsightedness can be corrected by using spectacles with a concave lens.
संबंधित प्रश्न
What is myopia?
the biological/technical terms for the lens of eye losing flexibility resulting in a kind of long-sightedness in middle aged people.
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.
Name the defect of vision in a person:
whose near point is more than 25 on away.
Name the defect of vision in a person:
whose far point is less than infinity
What is the other name for
myopia
What is the other name for
hypermetropia
What is the scientific name of
long-sightedness?
Name the defect of vision which makes the eye-lens cloudy resulting in blurred vision.
What is the far point of a person suffering from myopia (or short-sightedness)?
A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard.
Name the type of defect he is suffering from.
The defect of vision which cannot be corrected by using spectacles is:
(a) myopia
(b) presbyopia
(c) cataract
(d) hypermetropia
A person cannot see the distant objects clearly (though he can see the nearby objects clearly). He is suffering from the defect of vision called:
(a) cataract
(b) hypermetropia
(c) myopia
(d) presbyopia
Though a woman can see the distant object clearly, she cannot see the nearby objects clearly. She is suffering from the defect of vision called:
(a) long-sight
(b) short-sight
(c) hind-sight
(d) mid-sight
Name an old age eye defect. What happens in it?
Describe the mechanism of focusing the image of a distant object in your eye when you raise your head after reading a book.
You do not enjoy watching a movie from a very short distance from the screen in a cinema hall. Why?
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?
Anuja cannot see the blackboard writing but she can see nearby things.
(a) What is the eye defect she is suffering from?
(b) State the possible reason for her defect.
(c) How is it corrected
Give Reason:
Older people require glasses to read and write.
Draw a neat labeled diagram to show how hypermetropia can be rectified.
Explain the Term: 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.
Choose the Odd One Out:
In Myopia the human eye _______.
Nearsightedness: elongated eyeball : : farsightedness: _______
Assertion: Myopia is the defect of vision in which a person cannot see distant objects clearly.
Reason: This due to eye-ball being too short.
A person needs a lens of power –4.5 D for correction of her vision.
- What kind of defect in vision is she suffering from?
- What is the focal length of the corrective lens?
- What is the nature of the corrective lens?
When do we consider a person to be myopic or hypermetropic? Explain using diagrams how the defects associated with myopic and hypermetropic eye can be corrected?
Correlate the given sequence:
Hypermetropia : Convex lens : ______ : Concave lens
Observe the figure whether it is correct or not and explain the phenomenon.
Observe the figure and answer the following questions:
- Name the defect of vision represented in the above figure.
- State the reasons for this defect.
- How is it corrected?
- Draw the diagram to show the correction of this defect.
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.
Name the following:
Two kinds of accomodations.
