Physics - Section 3
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Spherical aberration occurs because spherical surfaces are not the ideal shape for a lens but are by far the simplest shape to which glass can be ground and polished, and so are often used. Spherical aberration causes beams parallel to, but distant from, the lens axis to be focused in a slightly different place than beams close to the axis. This manifests itself as a blurring of the image.
The first jet aircraft was the German Heinkel He 178 in 1939. The first jet airliner, the de Havilland Comet, was introduced in 1952.
The Boeing 707, the first widely successful commercial jet, was in commercial service for more than 50 years, from 1958 to 2010.
The light-year is most often used when expressing distances to stars and other distances on a galactic scale, especially in non-specialist and popular science publications.
The unit usually used in professional astrometry is the parsec (symbol: pc, approximately 3.26 light-years; the distance at which one astronomical unit subtends an angle of one second of arc).
Fluorocarbons and their derivatives are useful fluoropolymers, refrigerants, solvents, and aesthetics.
Anaesthetics are categorized into two classes: general anaesthetics, which cause a reversible loss of consciousness, and local anaesthetics, which cause a reversible loss of sensation for a limited region of the body while maintaining consciousness.
Combinations of anaesthetics are sometimes used for their synergistic and additive therapeutic effects. Adverse effects, however, may also be increased.
Transformers for use at power or audio frequencies typically have cores made of high permeability silicon steel.
The steel has a permeability many times that of free space and the core thus serves to greatly reduce the magnetizing current and confine the flux to a path which closely couples the windings.
Radar is an object-detection system that uses radio waves to determine the range, altitude, direction, or speed of objects.
It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain.
The radar dish transmits pulses of radio waves or microwaves that bounce off any object in their path. The object returns a tiny part of the wave's energy to a dish or antenna that is usually located at the same site as the transmitter.
A mirage is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky.
Mirages can be categorized as "inferior" (meaning lower), "superior" (meaning higher) and "Fata Morgana", one kind of superior mirage consisting of a series of unusually elaborate, vertically stacked images, which form one rapidly changing mirage.
An adiabatic process is one that occurs without transfer of heat or matter between a thermodynamic system and its surroundings. In an adiabatic process, energy is transferred only as work
Rarefaction is the reduction of an item’s density, the opposite of compression.
A convex mirror forms a virtual, diminished and upright image of an object. A concave lens always form an image which is Virtual and erect
Solid wastes produced from coating lines are disposed of in three ways: (l) incineration, (2) landfill, and (3) stockpiling.