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Diagram of the light path in an afocal system In optics , an afocal system (a system without focus) is an optical system that produces no net convergence or divergence of the beam, i.e., has an infinite effective focal length . [ 1 ]
Afocal photography works with any system that can produce a virtual image of parallel light, for example telescopes and microscopes. Afocal photographic setups work because the imaging device's eyepiece produces collimated light and with the camera's lens focused at infinity, creating an afocal system with no net convergence or divergence in the light path between the two devices. [2]
Diagram of a lamp reflector, showing path that light typically takes from a light source. Umbrella - studio flash. Similar to a domestic lampshade , these reflectors are fixed to an artificial light source (for example, a filament bulb or flash tube) to direct and shape the otherwise scattered light, reflecting it off their concave inner ...
Fig. 1: Fermat's principle in the case of refraction of light at a flat surface between (say) air and water. Given an object-point A in the air, and an observation point B in the water, the refraction point P is that which minimizes the time taken by the light to travel the path APB.
Concentration of light, especially sunlight, can burn. The word caustic, in fact, comes from the Greek καυστός, burnt, via the Latin causticus, burning. A common situation where caustics are visible is when light shines on a drinking glass. The glass casts a shadow, but also produces a curved region of bright light.
A light ray is a line or curve that is perpendicular to the light's wavefronts (and is therefore collinear with the wave vector). A slightly more rigorous definition of a light ray follows from Fermat's principle, which states that the path taken between two points by a ray of light is the path that can be traversed in the least time. [1]
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Light path in a meniscus telescope (Maksutov–Cassegrain) Maksutov–Cassegrain telescopes are the most commonly seen design that uses a meniscus corrector, a variant of the Maksutov telescope. It has a silvered "spot" secondary on the corrector, making a long focal length but compact (folded optical path) telescope with a narrow field of view.