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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
Define and describe the magnifying power of an optical instrument.
Answer the following question in detail.
How does magnifying power differ from linear or lateral magnification?
Answer the following question in detail.
What is a terrestrial telescope and an astronomical telescope?
Answer the following question in detail.
Obtain the expressions for magnifying power and the length of an astronomical telescope under normal adjustments.
Answer the following question in detail.
What is the limitation in increasing the magnifying powers of a simple microscope?
What is the near point focusing?
What are the advantages and disadvantages of using a reflecting telescope?
What is the use of an erecting lens in a terrestrial telescope?
What is the use of collimator in a spectrmeter?
What is myopia?
What is the remedy of myopia?
Explain the preliminary adjustments of the spectrometer.
Explain the experimental determination of the material of the prism using a spectrometer.
The near point and the far point for a person are 50 cm and 500 cm, respectively. Calculate the power of the lens the person should wear to read a book held in hand at 25 cm. What maximum distance is clearly visible for the person with this lens on the eye?
When a convex lens of 12.5 cm focal length is used as a magnifying glass, normal eye can see an object clearly at a distance of 25 cm. The magnifying power of the instrument is ____________.
If astronomical telescope of length 1.53 m has magnifying power of magnitude 50, the values of fo and fe are ____________.
In the adjoining figure, AB represents the incident ray, and BK is the reflected ray. If angle BCF = θ, then ∠BFP is given by ______.
A camera objective has an aperture diameter of d. If the aperture is reduced to diameter d/2, the exposure time under identical conditions of light should be made ______.
