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Consequently, a gravitational lens has no single focal point, but a focal line. The term "lens" in the context of gravitational light deflection was first used by O. J. Lodge, who remarked that it is "not permissible to say that the solar gravitational field acts like a lens, for it has no focal length". [11]
While gravitational lensing preserves surface brightness, as dictated by Liouville's theorem, lensing does change the apparent solid angle of a source. The amount of magnification is given by the ratio of the image area to the source area. For a circularly symmetric lens, the magnification factor μ is given by
Gravitational lensing is an effect of gravitation, most commonly associated with General relativity Wikimedia Commons has media related to Gravitational lensing . Subcategories
Strong gravitational lensing is a gravitational lensing effect that is strong enough to produce multiple images, arcs, or Einstein rings. Generally, for strong lensing to occur, the projected lens mass density must be greater than the critical density , that is Σ c r {\displaystyle \Sigma _{cr}} .
The iPhone 11 and 11 Pro series introduced an ultrawide lens; the latter two became the first triple-camera iPhones. The 11 has a dual-lens setup, lacking the telephoto lens of the 11 Pro and 11 Pro Max. The front camera is now capable of recording video at 4K as a result of a new 12 MP sensor, and can also capture slow-motion footage.
English: Optical geometry of a gravitational lens where, is the bending angle, is the actual angle subtended (without lens effect) by the source at the observer, is the observed angle subtended (due to lens effect) by the apparent source at the observer,
An Einstein Ring is a special case of gravitational lensing, caused by the exact alignment of the source, lens, and observer. This results in symmetry around the lens, causing a ring-like structure. [2] The geometry of a complete Einstein ring, as caused by a gravitational lens. The size of an Einstein ring is given by the Einstein radius.
The first such gravitational lens to be discovered was the double-imaged quasar Q0957+561 (or Twin Quasar) in 1979. [75] An example of a triply lensed quasar is PG1115+08. [ 76 ] Several quadruple-image quasars are known, including the Einstein Cross and the Cloverleaf Quasar , with the first such discoveries happening in the mid-1980s.