14 Facts About Optical lens

Typically the Optical lens axis passes through the physical centre of the Optical lens, because of the way they are manufactured.

The beam, after passing through the Optical lens, appears to emanate from a particular point on the axis in front of the Optical lens.

Conversely, a positive meniscus Optical lens has a steeper convex surface and is thicker at the centre than at the periphery.

The plane perpendicular to the Optical lens axis situated at a distance f from the Optical lens is called the focal plane.

Since the diverging light rays emanating from the Optical lens never come into focus, and those rays are not physically present at the point where they appear to form an image, this is called a virtual image.

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Lenses do not form perfect images, and a Optical lens always introduces some degree of distortion or aberration that makes the image an imperfect replica of the object.

Spherical aberration occurs because spherical surfaces are not the ideal shape for a Optical lens, but are by far the simplest shape to which glass can be ground and polished, and so are often used.

For instance, a plano-convex Optical lens, which is used to focus a collimated beam, produces a sharper focal spot when used with the convex side towards the beam source.

Coma occurs when an object off the optical axis of the lens is imaged, where rays pass through the lens at an angle to the axis ?.

Rays passing through the outer margins of the Optical lens are focused at different points, either further from the axis or closer to the axis .

Fresnel lens has its optical surface broken up into narrow rings, allowing the lens to be much thinner and lighter than conventional lenses.

Bifocal Optical lens has two or more, or a graduated, focal lengths ground into the Optical lens.

Gradient index lens has flat optical surfaces, but has a radial or axial variation in index of refraction that causes light passing through the lens to be focused.

Single convex Optical lens mounted in a frame with a handle or stand is a magnifying glass.