The first term in the next equation is Coulomb's law for a pair of ions, the second term is the short-range repulsion explained by Pauli's exclusion principle and the final term is the dispersion interaction term.

The electron optical system ( see fig. 14-1 ) is based in principle on the focusing action of concentric spherical cathode and anode surfaces.

The transmission electron microscope works on the same principle as an optical microscope but uses electrons in the place of light and electromagnets in the place of glass lenses.

PAO would use the principle of phased-array millimeter technology but at optical wavelengths.

However, this version of the principle is not general ; a more modern statement of the principle is that rays of light traverse the path of stationary optical length with respect to variations of the path.

See diagram below for its working principle and tunable optical filter devices

Working principle of a tunable optical filter based on rotating interference filter.

Fermat's principle states that the path light takes between two points is the path that has the minimum optical path length.

At the heart of Fresnel's wave theory is the Huygens-Fresnel principle, which states that every unobstructed point of a wavefront becomes the source of a secondary spherical wavelet and that the amplitude of the optical field E at a point on the screen is given by the superposition of all those secondary wavelets taking into account their relative phases.

The Greek philosopher Aristotle ( 384 to 322 BCE ) understood the optical principle of the pinhole camera.

In the second part of his 1924 thesis, de Broglie used the equivalence of the mechanical principle of least action with Fermat's optical principle: " Fermat's principle applied to phase waves is identical to Maupertuis ' principle applied to the moving body ; the possible dynamic trajectories of the moving body are identical to the possible rays of the wave.

The procedure for capturing a fingerprint using a sensor consists of rolling or touching with the finger onto a sensing area, which according to the physical principle in use ( optical, ultrasonic, capacitive or thermal ) captures the difference between valleys and ridges.

In other types of optical system, such as telescopes and binoculars, the same principle holds: the greater the focal ratio, the fainter the images created ( measuring brightness per unit area of the image ).

A related problem is posed by Fermat's principle: light follows the path of shortest optical length connecting two points, where the optical length depends upon the material of the medium.

While in principle a simple convex lens will suffice, in practice a compound lens made up of a number of optical lens elements is required to correct ( as much as possible ) the many optical aberrations that arise.

The operating principle enables optical laser technology to deliver highly accurate flow data, even in challenging environments which may include high temperature, low flow rates, high pressure, high humidity, pipe vibration and acoustic noise.

Aberrations can be explained by geometrical optics and can in principle be solved by increasing the optical quality — and cost — of the system.

This optical illusion is based in the principle that the human eye is capable of perceiving movement from pieces of information, for example, a succession of images.

In 1978 scientists at BMI-TNO, the research unit of Netherlands Organization for Applied Scientific Research at The University of Amsterdam, invented and patented a series of additional key elements to make the volume clamp work in clinical practice, among them: the use of modulated infra-red light in the optical system inside the sensor, the light-weight, easy to wrap finger cuff with Velcro fixation, a new pneumatic proportional control valve principle and last but not least the invention of a setpoint strategy for the determination and tracking of the correct volume at which to clamp the finger arteries – the Physiocal system.

The standard fiber optical trap relies on the same principle as the optical trapping, but with the Gaussian laser beam delivered through an Optical fiber.

The concept was similar in principle to the bucket-brigade device ( BBD ), which was developed at Philips Research Labs during the late 1960s.

The first experimental device demonstrating the principle was a row of closely spaced metal squares on an oxidized silicon surface electrically accessed by wire bonds.

The trammel of Archimedes or ellipsograph is a mechanical device that implements this principle.

The underlying principle was noted by the inventor of the first programmable computing device design:

He claims to demonstrate that because knowledge can only be had through contingent ( imperfect ) experience, the notion of absolute, uncontingent knowledge must not actually be obtainable, but must function merely as a “ regulative principle ” or heuristic device for problem solving.

Bayesian methods would suggest that one hypothesis was more probable than the other, but individual Bayesians might differ about which was the more probable and by how much, by virtue of having used different priors ; but that's the same thing as disagreeing on significance levels, except significance levels are just an ad hoc device which are not really a probability, while priors are not only justified by the rules of probability, but there is definitely a normative methodology to define beliefs ; so even if a Bayesian wanted to express complete ignorance ( as a frequentist claims to do but does it wrong ), they could do it with the maximum entropy principle.

e. " Today, we think of the principle of parsimony as a heuristic device.

That decision established the principle that customers could connect any lawful device to the telephone network, even to offer a competing service.

The new device used metal cards similar in principle to computer punched cards, and they were rapidly scanned as they fell past a light beam.

Some cooling towers operate on this principle ; similarly the solar updraft tower is a proposed device to generate electricity based on the stack effect.

The main disadvantage of basing a carburetor's operation on Bernoulli's principle is that, being a fluid dynamic device, the pressure reduction in a venturi tends to be proportional to the square of the intake air speed.

The most common rich mixture device for starting cold engines was the choke, which works on the same principle.

No irreversible computing device can use less energy than this, even in principle.

The technology gained further public attention when a company announced in early 2008 that they were close to fielding a device called MEDUSA ( Mob Excess Deterrent Using Silent Audio ) based on the principle.

It is also the guiding principle behind devices like the several Chinese Buddhist music boxes that loop chanting of mantras, which in turn was the inspiration of the Buddha machine, an ambient-music generating device.

The basic principle that allows the device to operate is the fact that a caesium atom can exist in any of nine energy levels, which can be informally thought of as the placement of electron atomic orbitals around the atomic nucleus.

The lighted stylet is a device that employs the principle of transillumination to facilitate blind orotracheal intubation ( an intubation technique in which the laryngoscopist does not view the glottis ).

The veiled head of Horatius could also be explained as an apotropaic device if one considers the tigillum the iugum of Juno, the feminine principle of fecundity.

Dumbo is based upon a children's story written by Helen Aberson and illustrated by Harold Pearl that was prepared to demonstrate the prototype of a toy storytelling display device called Roll-A-Book, which was similar in principle to a panorama.

In principle, a user or third party could install a standard AT expansion card, but since this required the writing of a special device driver, in practice this was very rare.

The doctrine of the pre-established harmony also loses its metaphysical significance – while remaining an important heuristic device – and the principle of sufficient reason introduced by Leibniz is once more discarded in favor of the principle of contradiction which Wolff seeks to make the fundamental principle of philosophy.

The device utilises an algorithm that is based on the principle that pulse pressure ( PP ) is proportional to stroke volume ( SV ).

Aristotle described the story of Thales, a poor philosopher from Miletus who developed a " financial device, which involves a principle of universal application ".