Advertisements
Advertisements
प्रश्न
What is astigmatism? What is its remedy?
Advertisements
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.
APPEARS IN
संबंधित प्रश्न
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.
What is a terrestrial telescope and an astronomical telescope?
Answer the following question in detail.
What is the limitation in increasing the magnifying powers of a simple microscope?
Discuss about simple microscope and obtain the equations for magnification for near point focusing and normal focusing.
Why is oil-immersed objective preferred in a microscope?
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 hypermetropia?
What is presbyopia?
Discuss about astronomical telescope.
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?
The magnifying power of a telescope is high if its objective and eyepiece have respectively ______.
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:
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 ______.
