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  2. Optical power - Wikipedia

    en.wikipedia.org/wiki/Optical_power

    Converging lenses have positive optical power, while diverging lenses have negative power. When a lens is immersed in a refractive medium, its optical power and focal length change. For two or more thin lenses close together, the optical power of the combined lenses is approximately equal to the sum of the optical powers of each lens: P = P 1 ...

  3. Beam divergence - Wikipedia

    en.wikipedia.org/wiki/Beam_divergence

    where f is the focal length of the lens. [1] Note that this measurement is valid only when the beam size is measured at the rear focal plane of the lens, i.e. where the focus would lie for a truly collimated beam, and not at the actual focus of the beam, which would occur behind the rear focal plane for a divergent beam.

  4. Vergence (optics) - Wikipedia

    en.wikipedia.org/wiki/Vergence_(optics)

    The vergence is inversely proportional to the distance from the focus in metres. If a (positive) lens is focussing the beam, it has to sit left of the focus, while a negative lens has to sit right of the focus to produce the appropriate vergence. In optics, vergence is the angle formed by rays of light that are not perfectly parallel to

  5. Optics - Wikipedia

    en.wikipedia.org/wiki/Optics

    A device that produces converging or diverging light rays due to refraction is known as a lens. Lenses are characterized by their focal length: a converging lens has positive focal length, while a diverging lens has negative focal length. Smaller focal length indicates that the lens has a stronger converging or diverging effect.

  6. Barlow lens - Wikipedia

    en.wikipedia.org/wiki/Barlow_lens

    Cone of light behind an achromatic doublet objective lens (A) without (red) and with (green) a Barlow lens optical element (B). The Barlow lens, named after Peter Barlow, is a diverging lens which, used in series with other optics in an optical system, increases the effective focal length of an optical system as perceived by all components that are after it in the system.

  7. Geometrical optics - Wikipedia

    en.wikipedia.org/wiki/Geometrical_optics

    Thin lenses produce focal points on either side that can be modeled using the lensmaker's equation. [5] In general, two types of lenses exist: convex lenses, which cause parallel light rays to converge, and concave lenses, which cause parallel light rays to diverge. The detailed prediction of how images are produced by these lenses can be made ...

  8. Lens - Wikipedia

    en.wikipedia.org/wiki/Lens

    A burning apparatus consisting of two biconvex lens. A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction.A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis.

  9. Virtual image - Wikipedia

    en.wikipedia.org/wiki/Virtual_image

    This is observed in ray tracing for a multi-lenses system or a diverging lens. For the diverging lens, forward extension of converging rays toward the lens will meet the converging point, so the point is a virtual object. For a (refracting) lens, the real image of an object is formed on the opposite side of the lens while the virtual image is ...