A person suffering from presbyopia needs bifocal lens. If he needs two lens of power −4·0 dioptre and + 2·0 dioptre, which one of these two lenses is for the correction of distant vision and what is its focal length ?

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TextPresbyopiaCorrection of Vision Defects Using LensesPower of a LensCBSE PYQ

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An old person is suffering from an eye defect caused by weakening of ciliary muscles and diminishing flexibility of the eye lens. If the defect of vision is 'a' which can be corrected by lens 'b', then 'a' and 'b' respectively are :

MCQ (Single)PresbyopiaCorrection of Vision Defects Using Lenses

The power of a lens 'X' is – 2·5 D. Name the lens and determine its focal length in cm. For which eye defect of vision will an optician prescribe this type of lens as a corrective lens ?

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Refraction Through Rectangular Glass Slab

Image Formation by Convex Lens

Image Formation by Concave Lens

Sign Convention for Spherical Lenses

Myopia or Near-sightedness

Correction of Vision Defects Using Lenses

Magnification by Spherical Lenses

Power of a Lens

"The value of magnification 'm' for a lens is – 2." Using new Cartesian Sign Convention and considering that an object is placed at a distance of 20 cm from the optical centre of this lens, state :

CASE_STUDIESRefraction Through Rectangular Glass SlabImage Formation by Convex LensImage Formation by Concave LensSign Convention for Spherical LensesMyopia or Near-sightednessCorrection of Vision Defects Using LensesLens Formula and Magnification for Thin LensesMagnification by Spherical LensesPower of a Lens

The numerical values of the focal lengths of two lenses A and B are 10 cm and 20 cm respectively. Which one of the two will show higher degree of convergence/divergence ? Give reason to justify your answer.

TextRefraction Through Rectangular Glass SlabImage Formation by Convex LensImage Formation by Concave LensSign Convention for Spherical LensesMyopia or Near-sightednessCorrection of Vision Defects Using LensesMagnification by Spherical LensesPower of a Lens

Draw a ray diagram to show the refraction of a ray of light through a rectangular glass slab when it falls obliquely from air into glass.

TextRefraction Through Rectangular Glass SlabImage Formation by Convex LensImage Formation by Concave LensSign Convention for Spherical LensesMyopia or Near-sightednessCorrection of Vision Defects Using LensesMagnification by Spherical LensesPower of a Lens

State Snell's law of refraction of light.

TextRefraction Through Rectangular Glass SlabImage Formation by Convex LensImage Formation by Concave LensSign Convention for Spherical LensesMyopia or Near-sightednessCorrection of Vision Defects Using LensesSnell's Law and Laws of Refraction of LightMagnification by Spherical LensesPower of a Lens