Dictionary tag: U-V-W-X-Y-Z

Workflow

A workflow is a series of tasks arranged in a specific order to achieve a goal effectively and efficiently.

  • By planning and organizing a workflow, you can ensure no important steps are missed and that the process runs smoothly.
    This can save time, reduce errors, and lead to consistent results.
  • A successful workflow requires careful assembly and organization of all resources beforehand so that they can be structured into a step-by-step procedure.
  • A typical colour management workflow might begin by ensuring that colours viewed through a camera viewfinder are captured and digitally recorded.
  • Image editing software such as Adobe CC might then be used to work through a decision-making process to ensure an image is fit for purpose.
  • A successful outcome is achieved when the final image accurately represents all decisions made during the editing process.

Weak Nuclear force

The weak nuclear force is one of the four fundamental forces in nature, alongside the electromagnetic force, the strong nuclear force, and gravity. The weak nuclear force played a key role in the creation of elements like hydrogen, helium, and lithium in the early universe. Today, it plays a critical role in the nuclear fusion reactions that power the Sun and other stars. The weak nuclear force is responsible for the decay of radioactive isotopes, as well as for other nuclear reactions such as beta decay and neutrino interactions.

  • When unstable radioactive isotopes decay, they emit radiation and transform into more stable elements.
  • In beta decay, a neutron in the nucleus of an atom decays into a proton, an electron, and an antineutrino. Neutrino interactions occur in nuclear reactors.
  • Neutrinos are very light particles that rarely interact with matter, but they can interact with the nuclei of atoms through the weak nuclear force.
  • The weak nuclear force is unique compared to other fundamental forces. It’s considered weak because its strength is significantly lower than other forces at the atomic level.
  • However, it has a longer range than the strong nuclear force, which acts over very short distances within the nucleus.

Wavefront

Electromagnetic waves that are parallel, share a common starting point, have the same frequency and phase, and move through the same medium, form an advancing wavefront at right angles to their direction of travel.

  • A wavefront is a conceptual tool used in to study waves, including electromagnetic waves like light. It refers to the locus of all points in phase with each other along the wave at a given instant. In other words, it represents the leading edge of a wave as it propagates through a medium.
    • Sources that emit light in all directions, known as point sources, generate spherical wavefronts.
    • Lasers, which produce a narrow beam of parallel rays, create waves with flat wavefronts.
    • An electromagnetic wave with a flat wavefront is known as a plane wave.
  • In addition to plane waves and spherical waves, there are also cylindrical waves produced when a point source is extended along a straight line.

Wave-particle duality

Wave-particle duality is a fundamental concept in quantum mechanics that describes the dual nature of particles, which can exhibit both wave-like and particle-like behaviour, depending on the situation.

  • For example, electromagnetic radiation (including light) is often described using wave properties, such as wavelength and frequency. However, when light interacts with matter, it behaves like discrete particles called photons.
  • A photon is the smallest quantum of electromagnetic radiation and represents a discrete packet of energy. When a photon is absorbed by matter, its energy becomes localized at specific points. This process is known as wave function collapse, which describes the transition of a quantum system from a superposition of possible states to a definite state when measured.
  • Wave-particle duality applies to all particles in quantum mechanics, not just light. Particles such as electrons also exhibit both wave-like and particle-like behaviour, depending on experimental conditions.

Wave function

In Quantum Mechanics, a wave function is a mathematical function that describes the quantum state of a physical system, such as a particle or a collection of particles.

  • A wave function provides information about the probabilities of the various possible states that a system might be in. It depends on the coordinates of the particles in the system (for example, position or momentum). It calculates the probability of finding the system in a particular state.
  • Wave functions determine the probability of various outcomes in quantum experiments.
  • In the context of quantum mechanics, a wave function encapsulates a wealth of information about a quantum system, including its possible states, probabilities, and how it evolves.

Wave

A wave is a disturbance that travels through a medium or space, transporting energy from one point to another. Waves can travel through a medium, like waves rippling across a lake, or through space, like the electromagnetic waves that carry sunlight to Earth.

  • Electromagnetic waves are generally invisible to the human eye, the exception is the visible spectrum, with wavelengths between approximately 400 and 700 nanometres.
  • Beyond this range, whether the wavelengths are longer (as in radio and microwaves) or shorter (as in ultraviolet, X-rays, and gamma rays), our eyes cannot detect them.
  • Although we cannot see most electromagnetic waves, we can perceive some in other ways. For instance, infrared waves are felt as heat, and electric current (which produces electromagnetic waves) can cause a buzzing sensation in a wire or cause electrocution.

Visual perception

Visual perception is the human ability to see and understand our surroundings by virtue of the sensitivity of our eyes to wavelengths of light across the entire visible spectrum, from red to violet.

  • Visual perception is a complex process that relies on the intricate interaction between our eyes, the brain, and the interpretation of light signals. It enables us to perceive various visual attributes such as shapes, sizes, textures, depths, motions, and spatial relationships, all of which contribute to our comprehensive understanding and interpretation of the visual world around us.

Vision

Vision, the human visual system, is a complex interplay between various components of the eye, including the cornea, pupil, lens, iris, retina, and optic nerve. It collaborates to capture, focus, and convert light into electrical signals that are transmitted to the brain for visual processing and interpretation.

  • Vision begins when light emitted or reflected by an object or scene enters our eyes through the cornea, pupil, and lens.
  • The cornea and the lens work together to concentrate and focus light onto the retina, which is the photosensitive layer of cells at the back of the eyeball.
  • The iris, located between the cornea and the lens, regulates the amount of light reaching the retina. It also determines eye colour and controls the size of the pupil.
  • The retina plays a vital role in converting differences in the wavelength and brightness of incoming light into electrical signals.
  • The optic nerve, which exits at the back of the eye, carries these signals to the visual processing areas of the brain.

Visible spectrum

The visible spectrum is the range of wavelengths of the electromagnetic spectrum that correspond with all the different colours we see in the world.

  • As light travels through the air it is invisible to our eyes.
  • Human beings don’t see wavelengths of light, but they do see the spectral colours that correspond with each wavelength and colours produced when different wavelengths are combined.
  • The visible spectrum includes all the spectral colours between red and violet and each is produced by a single wavelength.
  • The visible spectrum is often divided into named colours, though any division of this kind is somewhat arbitrary.
  • Traditional colours referred to in English include red, orange, yellow, green, blue, and violet.

Visible light

Visible light refers to the range of wavelengths of electromagnetic radiation that is perceived as colour by human observers. While the range of visible light is generally considered to be 400-700 nm, the exact range of colours perceptible can vary slightly between individuals.

  • Visible light is one form of electromagnetic radiation. Other forms of electromagnetic radiation include radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays. Visible light ranges from approximately 400 nanometres (nm) for violet to 700 nm for red.
  • A human observer perceives visible light as a combination of all the spectral colours between red and violet, as well as a vast range of other colours produced from the blending of different wavelengths in varying proportions.

Virtual photon

A virtual photon is a theoretical concept in particle physics. Virtual photons are thought to be particles that exist for an incredibly brief time and cannot be directly observed. Their existence is inferred through their role in mediating interactions between other particles.

  • Virtual photons are created when two charged particles interact with each other. For example, when two electrons interact with each other, they can exchange a virtual photon. This exchange of a virtual photon causes the electrons to repel each other. The electric force that we observe is thought to be due to the exchange of virtual photons between charged particles.
  • Virtual photons are thought to play a role in many different physical phenomena, including the electromagnetic force, the weak force, and the strong force.
  • More generally, a photon is a particle that carries electromagnetic radiation. It is the fundamental unit of light.

Viewing angle

When looking at a rainbow, the viewing angle is the angle between a line extended from an observer’s viewpoint to the bow’s anti-solar point and a second line extended towards the coloured arcs of its bow.

  • Viewing angle, angular distance and angle of deflection all produce the same value measured in degrees.
  • To locate the viewing angle as you look at a rainbow, trace two lines away from your eyes, one to the anti-solar point (the centre of the rainbow) and the other to one of the coloured arcs of the rainbow. The viewing angle is between those two lines, which intersect within the lenses of your eyes.
  • To establish where the anti-solar point of a rainbow is, imagine extending the ends of the bow until they meet and form a circle. The anti-solar point is right in the middle and is always below the horizon.
  • The coloured arcs of a rainbow form the circumference of circles (discs or cones) and share centres at their anti-solar point.
  • The viewing angle is the same whatever point is selected on the section of the circumference of the circular arcs of the rainbow visible above the horizon.
  • The viewing angle for a primary bow is between approx. 40.70 and 42.40 from its centre. The exact angle depends upon the rainbow colour selected.
  • The viewing angle for a secondary bow is between approx. 50.40 and 53.40 when you are looking at its centre.
  • The viewing angle can be calculated for any specific colour within a rainbow.
  • The centre of a rainbow is always on its axis. The rainbow axis is an imaginary straight line that connects the light source, observer and anti-solar point.
  • Most incident rays striking a raindrop will follow paths that place them outside the viewing angle. The resulting deflected rays pass by an observer and play no part in their observation.
  • The viewing angle for all rainbows is a constant determined by the laws of refraction and reflection.
  • The elevation of the Sun, the location of the observer and exactly where rain is falling are all variables that determine where a rainbow will appear.

Velocity

In the context of electromagnetic waves, velocity describes the rate of wave propagation, accounting for both magnitude (speed) and direction.

    • As a vector quantity, velocity provides a full description of the wave’s displacement over time, indicating how fast and in which direction it moves.
    • Velocity can be positive or negative, representing motion in different directions, and is measured in units such as meters per second (m/s), kilometres per hour (km/h), or miles per hour (mph), with an indication of direction.
  • In contrast, speed refers only to the magnitude of motion—how fast the wave travels—without regard to direction.
    • It is the magnitude of the displacement of an object per unit of time.
    • Speed does not consider the direction of motion, only the rate at which an object moves.
    • Speed is always positive or zero, representing the magnitude of motion.
    • Speed is measured in units such as meters per second (m/s), kilometres per hour (km/h), or miles per hour (mph).
  • Direction in the context of velocity is typically quantified by angles or coordinates relative to a reference point or axis.
    • For electromagnetic waves, this could be described using angles (e.g., degrees or radians) from a defined direction (such as the horizontal or vertical axis in a plane) or by using a coordinate system (such as Cartesian or polar coordinates) to specify the precise direction of wave propagation.

Work

In physics, work is defined as the transfer of energy that occurs when a force is applied to an object, causing it to move in the direction of the force. The amount of work done depends on the magnitude of the force, the distance the object moves, and the direction of the force relative to the movement.

  • Work is done when energy is transferred. For example, lifting a box transfers energy from your muscles to the box, giving it gravitational potential energy.
  • Work is measured in joules (J), where 1 joule is equivalent to 1 newton of force causing an object to move 1 meter.
  • Direction matters. If the force is in the same direction as the displacement, work is maximized (cos(0°) = 1). If the force is perpendicular, no work is done (cos(90°) = 0).
  • Examples related to work:
    • Pushing a car that rolls forward involves work because energy is transferred to the car, causing it to move.
    • Holding a heavy object stationary involves no work because, although force is applied, there’s no displacement.
  • The mathematical definition of work is:
    • Work=Force×Distance×cos⁡(θ)
    • Where:
      • Force is the applied force (in newtons, N).
      • Distance is the displacement of the object (in meters, m).
      • θ (theta) is the angle between the direction of the force and the direction of the displacement.

Visual processing

Visual processing

Visual processing is a complex and dynamic process that involves interactions between various retinal cells, neural pathways, and brain regions, ultimately leading to conscious visual perception.

Visual processing begins the moment light enters the human eye. It then progresses through multiple stages as signals travel towards the visual cortex, where the neural activity is integrated, resulting in conscious visual experience.

As visual processing begins the retina starts to process information about colors, as well as basic information about the shape and movement associated with those colors. By the end of this stage, multiple forms of information about a visual scene are ready to be conveyed to higher brain regions.

Let’s examine two major forms of processing, trichromatic and opponent-processing, which occur within the eyeball as visual information is gathered from light entering our eyes.

Trichromacy, also known as the trichromatic theory of colour vision, explains how three types of cone receptors in the retina work together with bipolar cells to perform their role in the initial stage of colour processing. Rod cells also play a significant role in this form of processing visual information, particularly in low-light conditions.

Opponent-processing, also known as the opponent-process theory of colour vision, explains the second form of processing. Opponent-processing involves ganglion cells that process the data received from trichromatic processing and combine it with other intercellular activities.

It is interesting to note that as both trichromatic and opponent-process theories developed over the last century, researchers and authors have often pitted one theory against the other. However, both processes are crucial for understanding how colour vision occurs.

Trichromatic theory explains the encoding of visual information when light hits the retina, while opponent-processing explains a subsequent stage of information convergence, assembly, and coding before the data leaves the retina via the optic nerve.

Note that:

  • Both trichromatic and opponent-processing occur independently within each retina, without comparing with the other.
  • Each eye gathers information from a specific viewpoint, approximately 50 mm to the left or right of the nose.
  • The two impressions are later compared and combined to provide us with a single three-dimensional, stereoscopic view of the world, rather than two flattened images.

We can consider the layers of retinal cells involved in trichromatic and opponent-processing as examining, interpreting, and transmitting visually relevant information. However, it would be incorrect to view this as a straightforward linear process due to the intricate neural networking, cross-referencing, and feedback loops within the retina.

Wavelength

Wavelength is the distance from any point on a wave to the corresponding point on the next wave. This measurement is taken along the middle line of the wave.

  • While wavelength can be measured from any point on a wave, it is often simplest to measure from the peak of one wave to the peak of the next, or from the bottom of one trough to the bottom of the next, ensuring the measurement covers a whole wave cycle.
  • The wavelength of an electromagnetic wave is usually given in metres.
  • The wavelength of visible light is typically measured in nanometres, with 1,000,000,000 nanometres making up a metre.
  • Each type of electromagnetic radiation – such as radio waves, visible light, and gamma waves – corresponds to a specific range of wavelengths on the electromagnetic spectrum.

Visual perception

Colour is not a property of electromagnetic radiation, but a feature of visual perception by an observer.

  • The human eye and so human visual perception are tuned to the visible spectrum and so to spectral colours between red and violet.
  • There are no properties of electromagnetic radiation that distinguish visible light from other parts of the electromagnetic spectrum.
  • Objects appear to be different colours to an observer depending on the wavelengths, frequencies and amplitude of visible light at the moment it strikes the retina at the back of the eye.

White light

White light is the term for visible light that contains all wavelengths of the visible spectrum at equal intensities.

  • The sun emits white light because sunlight contains all the wavelengths of the visible spectrum in roughly equal proportions.
  • Light travelling through a vacuum or a medium is termed white light if it includes all wavelengths of visible light.
  • Light travelling through a vacuum or air is not visible to our eyes unless it interacts with something.
  • The term white light can have two meanings:
    • It can refer to a combination of all wavelengths of visible light travelling through space, regardless of observation.
    • What a person sees when all colours of the visible spectrum hit a white or neutral-coloured surface.

Wave-cycle

A wave-cycle is the complete up-and-down motion of a wave, from one crest (peak) to the next crest, or from one trough (dip) to the next trough. Visualize a wave cycle as a series of points plotted along the path of a wave from one crest to the subsequent crest.

  • All electromagnetic waves have common characteristics like crests, troughs,, wavelength, frequency, amplitude, and propagation direction.
  • As a wave vibrates, a wave-cycle can be seen as a sequence of individual vibrations, measured from one peak to the next, one trough to the next, or from the start of one wave cycle to the start of the next.
  • A wave-cycle refers to the path from one point on a wave during a single oscillation to the same point on completion of that oscillation.
  • Wavelength meanwhile, is a measurement of the same phenomenon but in a straight line along the axis of the wave.

Wave diagram

A wave diagram is a graphic representation, using specific drawing rules and labels, that depicts variations in the characteristics of light waves. These characteristics include changes in wavelength, frequency, amplitude, speed of light and propagation direction.

  • A wave diagram provides a visual representation of how a wave behaves when interacting with various media or objects.
  • The purpose of a wave diagram is to illustrate optical phenomena, including reflection, refraction, dispersion, and diffraction.
  • Wave diagrams can be useful in both theoretical and practical applications, such as understanding the basics of the physics of light or when designing complex optical systems.

Visible spectrum

The visible part of the electromagnetic spectrum is called the visible spectrum.

  • The visible spectrum is the range of wavelengths of the electromagnetic spectrum that correspond with all the different colours we see in the world.
  • As light travels through the air it is invisible to our eyes.
  • Human beings don’t see wavelengths of light, but they do see the spectral colours that correspond with each wavelength and colours produced when different wavelengths are combined.
  • The visible spectrum includes all the spectral colours between red and violet and each is produced by a single wavelength.
  • The visible spectrum is often divided into named colours, though any division of this kind is somewhat arbitrary.
  • Traditional colours referred to in English include red, orange, yellow, green, blue, and violet.

Visible light

Visible light is the range of wavelengths of electromagnetic radiation perceived as colour by human observers.

  • Visible light is a form of electromagnetic radiation.
  • Other forms of electromagnetic radiation include radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays.
  • Visible light is perceived by a human observer as all the spectral colours between red and violet plus all other colours that result from combining wavelengths together in different proportions.
  • A spectral colour is produced by a single wavelength of light.
  • The complete range of colours that can be perceived by a human observer is called the visible spectrum.
  • The range of wavelengths that produce visible light is a very small part of the electromagnetic spectrum.