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  2. Gravitational lensing formalism - Wikipedia

    en.wikipedia.org/wiki/Gravitational_lensing...

    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 μ = θ β d θ d β {\displaystyle \mu ={\frac {\theta }{\beta }}{\frac {d\theta }{d\beta }}}

  3. Magnification - Wikipedia

    en.wikipedia.org/wiki/Magnification

    The postage stamp appears larger with the use of a magnifying glass. Stepwise magnification by 6% per frame into a 39-megapixel image. In the final frame, at about 170x, an image of a bystander is seen reflected in the man's cornea. Magnification is the process of enlarging the apparent size, not physical size, of

  4. Solid angle - Wikipedia

    en.wikipedia.org/wiki/Solid_angle

    The formula for the magnitude of the solid angle in steradians is =, where is the area (of any shape) on the surface of the sphere and is the radius of the sphere. Solid angles are often used in astronomy, physics, and in particular astrophysics. The solid angle of an object that is very far away is roughly proportional to the ratio of area to ...

  5. Lens - Wikipedia

    en.wikipedia.org/wiki/Lens

    Since ignition can be achieved even with a poorly made lens, lenses have been used as burning-glasses for at least 2400 years. [6] A modern application is the use of relatively large lenses to concentrate solar energy on relatively small photovoltaic cells, harvesting more energy without the need to use larger and more expensive cells.

  6. Angular resolution - Wikipedia

    en.wikipedia.org/wiki/Angular_resolution

    If the lens is focusing a beam of light with a finite extent (e.g., a laser beam), the value of D corresponds to the diameter of the light beam, not the lens. [Note 1] Since the spatial resolution is inversely proportional to D, this leads to the slightly surprising result that a wide beam of light may be focused on a smaller spot than a narrow ...

  7. Angular diameter - Wikipedia

    en.wikipedia.org/wiki/Angular_diameter

    (The Sun's diameter is 400 times as large and its distance also; the Sun is 200,000 to 500,000 times as bright as the full Moon (figures vary), corresponding to an angular diameter ratio of 450 to 700, so a celestial body with a diameter of 2.5–4″ and the same brightness per unit solid angle would have the same brightness as the full Moon.)

  8. Gravitational lens - Wikipedia

    en.wikipedia.org/wiki/Gravitational_lens

    A critique of the concept was given by Landis, [41] who discussed issues including interference of the solar corona, the high magnification of the target, which will make the design of the mission focal plane difficult, and an analysis of the inherent spherical aberration of the lens.

  9. Diffraction-limited system - Wikipedia

    en.wikipedia.org/wiki/Diffraction-limited_system

    For instance, for an f/8 lens (= and %) and for green light (= 0.5 μm wavelength) light, the focusing spot diameter will be d = 9.76 μm or 19.5. This is similar to the pixel size for the majority of commercially available 'full frame' (43mm sensor diagonal) cameras and so these will operate in regime 3 for f-numbers around 8 (few lenses are ...