A dioptre is the unit used to measure the optical power of a lens. It indicates how strongly a lens converges or diverges light. The optical power of a lens is the reciprocal of its focal length in meters. For... Read More
A dioptre is the unit used to measure the optical power of a lens. It indicates how strongly a lens converges or diverges light. The optical power of a lens is the reciprocal of its focal length in meters. For example, a lens with a focal length of 1 meter has a power of 1 dioptre (1 D), while a lens with a focal length of 0.5 meters has a power of 2 dioptres (2 D).
Dioptres are essential in optometry and ophthalmology, as they help prescribe glasses and contact lenses for correcting vision defects such as myopia (nearsightedness), hypermetropia (farsightedness), and astigmatism. A lens with a positive dioptre value is convex, used for farsightedness, while a negative value represents a concave lens, used for nearsightedness.
Other options in the MCQ are incorrect:
Current is measured in amperes, not dioptres.
Force is measured in newtons.
Focal length is measured in meters, but dioptre is derived from the focal length as its reciprocal, making it a measure of lens power rather than the distance itself.
The concept of dioptre helps students understand the practical relationship between lens curvature, focal length, and light refraction. It is widely used in eyeglasses, microscopes, cameras, and telescopes, where precise calculation of lens power is necessary to focus light correctly and obtain clear images.
Studying dioptres also reinforces basic principles of geometrical optics, including refraction, convergence, and divergence of light rays. Understanding this concept allows students to connect theoretical knowledge with real-life applications, demonstrating how physics principles are applied in everyday vision correction and optical instruments.
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