Human Eye and Colourful world

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The least distance of distinct vision for a normal healthy person is about 25 cm. This is the minimum distance at which we can see an object clearly without straining our eyes. At younger age (below 1…

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The angle of vision for a healthy human being is about 60°. This is the maximum angle at which we can see the whole object clearly. If the angle is above 60°, we can see only part of the object. The a…

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Accommodation is the ability of the eye lens to change its focal length by changing its shape. The ciliary muscles help the eye lens adjust its curvature to focus objects at different distances on the…

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Maximum focal length: When object is at infinity, f_max = 2.5 cm (distance from lens to retina) Minimum focal length: When object is at 25 cm, using lens formula: 1/f = 1/v - 1/u = 1/2.5 - 1/(-25) = 1…

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Myopia (near-sightedness) is a defect where a person cannot see distant objects clearly but can see nearby objects clearly. The maximum focal length is less than 2.5 cm, causing distant object images …

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Hypermetropia (far-sightedness) is a defect where a person can see distant objects clearly but cannot see nearby objects clearly. The minimum focal length is greater than 2.27 cm, causing nearby objec…

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Presbyopia is a vision defect that occurs with aging when the eye gradually loses its power of accommodation. The ciliary muscles weaken and the eye lens becomes less flexible, making it difficult to …

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Power of a lens is the degree of convergence or divergence of light rays that can be achieved by the lens. It is the reciprocal of focal length. Formula: P = 1/f (when f is in meters) or P = 100/f (wh…