Optics on the Web
Links to optics-related applets, tutorials and web sites of interest. NOTE: Some applets no longer work with the most recent Java. If possible, try running on an earlier version. In some cases, I've found alternate applets that are similar and that will run on most browsers (I use Chrome, Safari and Firefox). If you find a link that doesn't work, please email me. Applications of Optics in Communications (Fiber Optics), Manufacturing, Medicine (including the eye) and More Societies, Organizations and Online Magazines This site contains a huge collection of tutorials and applets covering most of an introductory optics course. This is an optics tutorial for chemistry students. optics tutorial with an ophthalmic slant, including how corrective lenses work
Interference (wave propagation)
Swimming Pool Interference[1] Interference of waves from two point sources. Magnified-image of coloured interference-pattern in soap-film. The black "holes" are areas where the film is very thin and there is a nearly total destructive interference. Consider, for example, what happens when two identical stones are dropped into a still pool of water at different locations. Geometrical arrangement for two plane wave interference Interference fringes in overlapping plane waves A simple form of interference pattern is obtained if two plane waves of the same frequency intersect at an angle. It can be seen that the two waves are in phase when and are half a cycle out of phase when Constructive interference occurs when the waves are in phase, and destructive interference when they are half a cycle out of phase. and df is known as the fringe spacing. The fringes are observed wherever the two waves overlap and the fringe spacing is uniform throughout. A point source produces a spherical wave. for to where
Numerical aperture
The numerical aperture with respect to a point P depends on the half-angle θ of the maximum cone of light that can enter or exit the lens. General optics[edit] In most areas of optics, and especially in microscopy, the numerical aperture of an optical system such as an objective lens is defined by is constant across an interface. In air, the angular aperture of the lens is approximately twice this value (within the paraxial approximation). In microscopy, NA is important because it indicates the resolving power of a lens. Numerical aperture is used to define the "pit size" in optical disc formats.[2] Numerical aperture versus f-number[edit] Numerical aperture is not typically used in photography. , which is defined as the ratio of the focal length to the diameter of the entrance pupil: This ratio is related to the image-space numerical aperture when the lens is focused at infinity.[3] Based on the diagram at the right, the image-space numerical aperture of the lens is: thus , and not where
Optical fiber cable
A TOSLINK optical fiber cable with a clear jacket. These cables are used mainly for digital audio connections between devices. An optical fiber cable is a cable containing one or more optical fibers. The optical fiber elements are typically individually coated with plastic layers and contained in a protective tube suitable for the environment where the cable will be deployed. Design[edit] A multi-fiber cable Left: LC/PC connectors Right: SC/PC connectors All four connectors have white caps covering the ferrules. For indoor applications, the jacketed fiber is generally enclosed, with a bundle of flexible fibrous polymer strength members like aramid (e.g. Fibre-optic cable in a Telstra pit An optical fiber breakout cable For use in more strenuous environments, a much more robust cable construction is required. A critical concern in outdoor cabling is to protect the fiber from contamination by water. Capacity and market[edit] Reliability and quality[edit] Cable types[edit] Jacket material[edit]
Diffraction
Diffraction pattern of red laser beam made on a plate after passing a small circular hole in another plate Diffraction refers to various phenomena which occur when a wave encounters an obstacle or a slit. In classical physics, the diffraction phenomenon is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings. These characteristic behaviors are exhibited when a wave encounters an obstacle or a slit that is comparable in size to its wavelength. Similar effects occur when a light wave travels through a medium with a varying refractive index, or when a sound wave travels through a medium with varying acoustic impedance. Diffraction occurs with all waves, including sound waves, water waves, and electromagnetic waves such as visible light, X-rays and radio waves. Richard Feynman[3] wrote: The formalism of diffraction can also describe the way in which waves of finite extent propagate in free space. Examples[edit] History[edit] where
Speckle pattern
Laser speckle on a digital camera image from a green laser pointer. This is a subjective speckle pattern. (Note that the color differences in the image are introduced by limitations of the camera system.) Explanation[edit] The speckle effect is a result of the interference of many waves of the same frequency, having different phases and amplitudes, which add together to give a resultant wave whose amplitude, and therefore intensity, varies randomly. , where is the mean intensity.[2] When a surface is illuminated by a light wave, according to diffraction theory, each point on an illuminated surface acts as a source of secondary spherical waves. If light of low coherence (i.e., made up of many wavelengths) is used, a speckle pattern will not normally be observed, because the speckle patterns produced by individual wavelengths have different dimensions and will normally average one another out. Subjective speckles[edit] This can be explained as follows. Objective speckles[edit] Reduction[edit]
Optical cavity
An optical cavity or optical resonator is an arrangement of mirrors that forms a standing wave cavity resonator for light waves. Optical cavities are a major component of lasers, surrounding the gain medium and providing feedback of the laser light. They are also used in optical parametric oscillators and some interferometers. Light confined in the cavity reflect multiple times producing standing waves for certain resonance frequencies. The standing wave patterns produced are called modes; longitudinal modes differ only in frequency while transverse modes differ for different frequencies and have different intensity patterns across the cross section of the beam. Different resonator types are distinguished by the focal lengths of the two mirrors and the distance between them. Optical cavities are designed to have a large Q factor;[1] a beam will reflect a very large number of times with little attenuation. Resonator modes[edit] Resonator types[edit] Spherical cavity[edit] Stability[edit]
