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प्रश्न
What is astigmatism? What is its remedy?
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उत्तर
- Astigmatism is the defect arising due to different curvatures along different planes in the eye lens.
- Astigmatic person cannot see in all the directions equally well. The defect due to astigmatism is more serious than myopia and hypermetropia.
- Astigmatism can be corrected using a lens which has different curvatures in different planes.
- In general, these specially made glasses with different curvature for different planes are called cylindrical lenses.
- Due to aging, people may develop a combination of more than one defect.
- If it is the combination of nearsightedness and farsightedness then, such persons may need a converging glass for reading purposes and a diverging glass for seeing at a distance.
- Bifocal lenses and progressive lenses provide solutions for these kinds of problems.
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संबंधित प्रश्न
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?
Why is oil-immersed objective preferred in a microscope?
What is the use of an erecting lens in a terrestrial telescope?
What is the use of collimator in a spectrmeter?
What are the uses of spectrometer?
What is the remedy of myopia?
Discuss about simple microscope and obtain the equations for magnification for near point focusing and normal focusing.
Discuss about astronomical telescope.
Mention different parts of the spectrometer.
Explain the preliminary adjustments of the 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?
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The speed of light in media 'A' and 'B' are 2.0 × 1010 cm/s and 1.5 × 1010 cm/s respectively. A ray of light enters from medium B to A at an incident angle 'θ'. If the ray suffers total internal reflection, then ______.
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 ______.
