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प्रश्न
What is presbyopia?
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उत्तर १
This defect is similar to hypermetropia i.e., a person having this defect cannot see nearby objects distinctly, but can see distant objects without any difficulty. This defect occurs in elderly persons (aged persons).
उत्तर २
Presbyopia is a vision disorder that develops with age, usually beyond 40. This condition causes a progressive loss of visual focus on close objects.
संबंधित प्रश्न
Answer the following question in detail.
How does magnifying power differ from linear or lateral magnification?
Answer the following question in detail.
Derive an expression for the magnifying power of a simple microscope. Obtain its minimum and maximum values in terms of its focal length.
Answer the following question in detail.
Obtain the expressions for magnifying power and the length of an astronomical telescope under normal adjustments.
What is the near point focusing?
Why is oil-immersed objective preferred in a microscope?
What is the use of an erecting lens in a terrestrial telescope?
What is the remedy of myopia?
What is hypermetropia?
What is the remedy of hypermetropia?
What is astigmatism? What is its remedy?
Discuss about simple microscope and obtain the equations for magnification for near point focusing and normal focusing.
A compound microscope has a magnifying power of 100 when the image is formed at infinity. The objective has a focal length of 0.5 cm and the tube length is 6.5 cm. What is the focal length of the eyepiece.
If astronomical telescope of length 1.53 m has magnifying power of magnitude 50, the values of fo and fe are ____________.
The magnifying power of a telescope is nine. When it is adjusted for parallel rays, the distance between the objective and eyepiece is 20 cm. The focal length of objective and eyepiece are respectively.
An object viewed from a near point distance of 25 cm, using a microscopic lens with magnification '6', gives an unresolved image. A resolved image is observed at infinite distance with a total magnification double the earlier using an eyepiece along with the given lens and a tube of length 0.6 m, if the focal length of the eyepiece is equal to ______ cm.
Magnification produced by astronomical telescope for normal adjustment is 10 and length of telescope is 1.1 m. The magnification when the image is formed at least distance of distinct vision (D = 25 cm) is ______.
An observer looks at a distant tree of height 10 m with a telescope of magnifying power of 20. To the observer the tree appears:
The image formed by an objective of a compound microscope is ______.
In the adjoining figure, AB represents the incident ray, and BK is the reflected ray. If angle BCF = θ, then ∠BFP is given by ______.
