Kinetic energy

Kinetic energy is the energy an object has because of its motion.

  • Objects move or change direction when a force is applied to them.
  • In physics, this process is said to involve ‘work’, so work is done whenever a force moves an object.
  • This application of force by one object to another involving work being done and results in kinetic energy being transferred from one place or one object to another.
  • Everything in the universe has kinetic energy because everything above absolute zero is in motion.
  • Planets moving through space, cars and people all contain potential energy and kinetic energy.
  • Kinetic energy is evident at an atomic scale as molecules vibrate when heat is applied to a substance, electrons move around an electrical circuit or light illuminates a room.
  • The human senses of sight, hearing and touch are tuned to different forms of kinetic energy.

An example of this might involve a person forcing a heavy bolder to roll up a hill. By the time they reach the top they feel exhausted by the effort because they have used up a lot of kinetic energy some of which has been transferred to the boulder. This energy might then be transferred to other boulders if it crashes back down the hill.

If the observer in this example is too heavy and doesn’t move, no energy is transferred to it. Work is still done but this time the energy is transferred between the person’s muscles etc. and released into the air in the form heat.

Lateral geniculate nucleus

The lateral geniculate nucleus is a relay centre on the visual pathway from the eyeball to the human brain. It receives a major sensory input from the retina via the axons of ganglion cells.

  • The thalamus which houses the lateral geniculate nucleus is a small structure within the brain, located just above the brain stem between the cerebral cortex and the midbrain and has extensive nerve connections to both.
  • The lateral geniculate nucleus is the central connection for the optic nerve to the occipital lobe, particularly the primary visual cortex.
  • Both the left and right hemispheres of the brain have a lateral geniculate nucleus.
  • There are three major cell types in the lateral geniculate nucleus which connect to three distinct types of ganglion cells:
    • P ganglion cells send axons to the parvocellular layer of the lateral geniculate nucleus.
    • M ganglion cells send axons to the magnocellular layer.
    • K ganglion cells send axons to a koniocellular layer.
  • The lateral geniculate nucleus specialises in calculations based on the information it receives from both the eyes and from the brain. Calculations include resolving temporal and spatial correlations between different inputs. This means that things can be organised in terms of the sequence of events over time and the relationship of things within the overall field of view.
  • Some of the correlations deal with signals received from one eye or the other. Some deal with the left and right semi-fields of view captured by both eyes. As a result, they help to produce a three-dimensional representation of the field of view of an observer.
  • Other important factors to note regarding the lateral geniculate nucleus are:
    • The lateral geniculate nucleus carries out many functions, some are directed towards the eyes, others are directed towards the brain.
    • A signal is provided to control the vergence of the two eyes so they converge at the principal plane of interest in object-space at any particular moment.
    • A signal is provided to control the focus of the eyes based on the calculated distance to the principal plane of interest.
    • Computations are achieved to determine the position of every major element in object-space relative to the principal plane. Through subsequent motion of the eyes, a larger stereoscopic mapping of the visual field is achieved.
    • A tag is provided for each major element in the central field of view of object-space. The accumulated tags are attached to the features in the merged visual fields and are forwarded to the primary visual cortex.
    • A tag is provided for each major element in the visual field describing the velocity of the major elements based on changes in position over time. The velocity tags (particularly those associated with the peripheral field of view) are also used to determine the direction the organism is moving relative to object-space.

https://en.wikipedia.org/wiki/Lateral_geniculate_nucleus

Law of refraction (Snell’s Law)

As light crosses the boundary between two transparent media, the law of refraction (Snell’s law) states the relationship between the angle of incidence and angle of refraction of the light with reference to the refractive indices of both media as follows:

When electromagnetic radiation (light) of a specific frequency crosses the interface of any given pair of media, the ratio of the sines of the angles of incidence and the sines of the angles of refraction is a constant in every case.

  • Snell’s law deals with the fact that for an incident ray approaching the boundary of two media, the sine of the angle of incidence multiplied by the index of refraction of the first medium is equal to the sine of the angle of refraction multiplied by the index of refraction of the second medium.
  • Snell’s law deals with the fact that the sine of the angle of incidence to the sine of the angle of refraction is constant when a light ray passes across the boundary from one medium to another.
  • Snell’s law can be used to calculate the angle of incidence or refraction associated with the use of lenses, prisms and other everyday materials.
  • When using Snell’s law:
    • The angles of incidence and refraction are measured between the direction of a ray of light and the normal – where the normal is an imaginary line drawn on a ray diagram perpendicular to, so at a right angle to (900), to the boundary between two media.
    • The wavelength of the incident light is accounted for.
    • The refractive indices used are selected for the pair of media concerned.
    • The speed of light is expressed in metres per second (m/s).

Law of refraction (Snell’s law)

As light crosses the boundary between two transparent media, the law of refraction (Snell’s law) states the relationship between the angle of incidence and angle of refraction of the light with reference to the refractive indices of both media as follows:

When electromagnetic radiation (light) of a specific frequency crosses the interface of any given pair of media, the ratio of the sines of the angles of incidence and the sines of the angles of refraction is a constant in every case.

  • Snell’s law deals with the fact that for an incident ray approaching the boundary of two media, the sine of the angle of incidence multiplied by the index of refraction of the first medium is equal to the sine of the angle of refraction multiplied by the index of refraction of the second medium.
  • Snell’s law deals with the fact that the sine of the angle of incidence to the sine of the angle of refraction is constant when a light ray passes across the boundary from one medium to another.
  • Snell’s law can be used to calculate the angle of incidence or refraction associated with the use of lenses, prisms and other everyday materials.
  • When using Snell’s law:
    • The angles of incidence and refraction are measured between the direction of a ray of light and the normal – where the normal is an imaginary line drawn on a ray diagram perpendicular to, so at a right angle to (900), to the boundary between two media.
    • The speed of light expressed in metres per second = 299,792,458 m/sec. So = 299,792 km/sec.

https://en.wikipedia.org/wiki/Snell%27s_law

LED

An LED (Light-emitting-diode) is an electroluminescent light source. It produces light by passing an electrical charge across the junction of a semiconductor.

Multi-colour LED’s typically contain three separate diodes that mix red, green and blue wavelengths to produce a full range of colours.

  • LED’s don’t produce white light in the same way that incandescent lamps do.
  • One LED cannot produce the full range of colours that sunlight or incandescent light produces.
  • A LED typically emits a single colour of light which is composed of a very narrow range of wavelengths.
  • However LED’s emitting the three primary colours of red, green and blue light can be combined to produce white light.
  • By changing the relative intensity of the primary colours, a multi-colour LED produces an extremely wide range of colours.
  • An LED light source is often used to demonstrate the effect of projecting primary coloured lights onto a dark surface because they emit light in very narrow bands of wavelengths. The peak wavelength for the selected lights might typically be red = 625 nanometres, green = 500 nm, blue = 440 nm.

https://en.wikipedia.org/wiki/Light-emitting_diode

Light

Light is electromagnetic radiation (radiant energy), which, detached from its source, is transported by electromagnetic waves (or their quanta, photons) and propagates through space. Even if humans had never evolved, electromagnetic radiation would have been emitted by stars since the formation of the first galaxies over 13 billion years ago.

  • Simply stated, light is energy. Light is the way energy travels through space.
  • Light and colour are entirely different phenomena. Whilst light is electromagnetic radiation, the experience of colour is a feature of human vision that depends first of all on the construction of our eyes and the wavelength, frequency and amplitude of visible light that strikes the retina.
  • The human eye, and so human perception, is tuned to the visible spectrum and so to spectral colours between red and violet. It is the sensitivity of the eye to this small part of the electromagnetic spectrum that results in the perception of colour.
  • Whilst the term light can be used to refer to the whole of the electromagnetic spectrum, visible light refers to the small range of wavelengths that our eyes are tuned to.
  • The term light can be used in three different ways:
  • Light can be used to mean the whole of the electromagnetic spectrum from radio waves, through visible light to gamma rays. When this meaning is intended, the terms radiant energy or photon energy are placed in brackets after the term light in this resource.
  • Light can be used to mean the range of wavelengths and frequencies that can be detected by the human eye. A better term is visible light which refers to the wavelengths that correspond with the colours between red and violet, the visible spectrum.
  • Light can also be used to mean the range of wavelengths and frequencies between infra-red and ultra-violet. This usage is sometimes useful because the outer limits of the visible spectrum can differ under different lighting conditions and for different individuals.

https://en.wikipedia.org/wiki/Light

Light

Light is electromagnetic radiation (radiant energy), which, detached from its source, is transported by electromagnetic waves (or their quanta, photons) and propagates through space. Even if humans had never evolved, electromagnetic radiation would have been emitted by stars since the formation of the first galaxies over 13 billion years ago.

  • Simply stated, light is energy. Light is the way energy travels through space.
  • Whilst the term light can be used to refer to the whole of the electromagnetic spectrum, visible light refers to the small range of wavelengths that our eyes are tuned to.
  • The term light can be used in three different ways:
  • Light can be used to mean the whole of the electromagnetic spectrum from radio waves, through visible light to gamma rays. When this meaning is intended, the terms radiant energy or photon energy are placed in brackets after the term light in this resource.
  • Light can be used to mean the range of wavelengths and frequencies that can be detected by the human eye. A better term is visible light which refers to the wavelengths that correspond with the colours between red and violet, the visible spectrum.
  • Light can also be used to mean the range of wavelengths and frequencies between infra-red and ultra-violet. This usage is sometimes useful because the outer limits of the visible spectrum can differ under different lighting conditions and for different individuals.

Light source

A light source is a natural or man-made object that emits one or more of wavelengths of light.

  • The Sun is the most important light source in our lives and emits every wavelength of light in the visible spectrum.
  • Celestial sources of light include other stars, comets and meteors.
  • Other natural sources of light include lightning, volcanoes and forest fires.
  • There are also bio-luminescent light sources including some species of fish and insects as well as types of bacteria and algae.
  • Man-made light sources of the most simple type include natural tars and resins, wax candles, lamps that burn oil, fats or paraffin and gas lamps.
  • Modern man-made light sources include tungsten light sources. These are a type of incandescent source which means they radiate light when electricity is used to heat a filament inside a glass bulb.
  • Halogen bulbs are more efficient and long-lasting versions of incandescent tungsten lamps and produce a very uniform bright light throughout the bulb’s lifetime.
  • Fluorescent lights are non-incandescent sources of light. They generally work by passing electricity through a glass tube of gas such as mercury, neon, argon or xenon instead of a filament. These lamps are very efficient at emitting visible light, produce less waste heat, and typically last much longer than incandescent lamps.
  • An LED (Light Emitting Diode) is an electroluminescent light source. It produces light by passing an electrical charge across the junction of a semiconductor.
  • Made-made lights can emit a single wavelength, bands of wavelengths or combinations of wavelengths.
  • An LED light typically emits a single colour of light which is composed of a very narrow range of wavelengths.

https://en.wikipedia.org/wiki/Light#Light_sources

Light source

A light source is a natural or man-made object that emits one or more of wavelengths of light.

  • The Sun is the most important light source in our lives and emits every wavelength of light in the visible spectrum.
  • Celestial sources of light include other stars, comets and meteors.
  • Other natural sources of light include lightning, volcanoes and forest fires.
  • There are also bio-luminescent light sources including some species of fish and insects as well as types of bacteria and algae.
  • Man-made light sources of the most simple type include natural tars and resins, wax candles, lamps that burn oil, fats or paraffin and gas lamps.
  • Modern man-made light sources include tungsten light sources. These are a type of incandescent source which means they radiate light when electricity is used to heat a filament inside a glass bulb.
  • Halogen bulbs are more efficient and long-lasting versions of incandescent tungsten lamps and produce a very uniform bright light throughout the bulb’s lifetime.
  • Fluorescent lights are non-incandescent sources of light. They generally work by passing electricity through a glass tube of gas such as mercury, neon, argon or xenon instead of a filament. These lamps are very efficient at emitting visible light, produce less waste heat, and typically last much longer than incandescent lamps.
  • An LED (Light Emitting Diode) is an electroluminescent light source. It produces light by passing an electrical charge across the junction of a semiconductor.
  • Made-made lights can emit a single wavelength, bands of wavelengths or combinations of wavelengths.
  • An LED light typically emits a single colour of light which is composed of a very narrow range of wavelengths.

Light stimulus

Light reaching the human eye is called a light stimulus because it stimulates the visual system.

  • Sometimes the term colour stimulus is used because the light stimulus produces the experience of colour for an observer. Every light stimulus can be described in terms of the composition and intensity of wavelengths of light that enter the eye.
  • Imagine, that at a specific moment, the wavelengths of a stimulus include reds, oranges, yellows, greens, blues and violets. The colour an observer sees depends on the response not only to the mixture of wavelengths that correspond with these colours but also to the intensity of the light at each wavelength.
  • In many situations, intensity varies progressively across a range of wavelengths and can be described by the spectral power distribution of the stimulus.

Luminance

The term luminance is used when talking about how illuminated objects appear to an observer.

  • Luminance is a measure of the intensity of light that reaches the eye.
  • So we can talk about:
    • The luminance desert sand under moonlight.
    • The luminance of a road surface under street lights.
    • The luminance of a book cover in sunshine.
  • Luminance can be measured and so is an objective term rather than a subjective experience.
  • The light produced by a table lamp can be described in terms of luminosity, the amount of light that is then reflected from a surface towards an observer can then be measured in terms of luminance.

https://en.wikipedia.org/wiki/Luminance

Luminosity

Luminosity is about light given off by a source such as the Sun or a light-bulb.

  • If one light bulb produces one unit of light, then two produces twice the luminosity and so on.
  • Because luminosity is about light being given off in all directions it is not something that an observer can see directly.
  • A light source’s luminosity depends on how much power it consumes. In the case of a light bulb, for example, it relates to the amount of electrical energy the bulb is burning and how much of that energy is being turned into visible light.
  • Luminosity is something that can be measured and so is an objective term.

 

  • If you have read about trichromatic vision, you will know that it is possible to match all the colours in the visible spectrum seen by an observer by appropriate mixing of wavelengths and intensities (luminosity) of light corresponding with three primary colours and this can be achieved without any loss of information so far as an observer is concerned.
  • Now imagine three light sources with wavelengths corresponding with red, green and blue connected to sliders that allows the luminosity of each component to be adjusted between a minimum of 0% (off) and a maximum of 100% (fully on).
  • Zero luminosity for each component means no light, so an observer in a windowless room would be in darkness. If each component is set to full luminosity our observer will see white. The exact quality of white depends on the type of lights, how accurately their wavelength is controlled and the surface the light falls upon.
  • If the sliders that control each light are set to the same value (and so to the same luminosity) between 1% and 99% then the result is a shade of grey, which appears darker as the intensity decreases or brighter as the intensity increases.
  • When the luminosity of each slider is set to different values, the result is the perception of a colour.
  • When one of the components has the highest luminosity, the colour will be a hue near that primary colour and so appear more reddish, greenish or bluish. When two components have the same high luminosity, then the observer sees the hue of a secondary colour (a shade of cyan, magenta or yellow).
  • Maximum luminosity of a spectral colour corresponds with its lightest tint.

 

  • Maximum luminosity of a display device corresponds with the brightest white it can reproduce and is called the white point.
  • The black point corresponds with the minimum luminosity of a device, so corresponds with the device being turned off.
  • The contrast ratio of maximum and minimum luminosity of a television or computer screen is typically more than 280:1

https://en.wikipedia.org/wiki/Adobe_RGB_color_space

Magnetic field

A magnetic field is created when electric current flows. The greater the current the stronger the magnetic field.

  • Whilst a magnetic field is created when an electric current flows, an electric field is created by a change in voltage (charge). The higher the voltage the stronger the field.
  • An electromagnetic wave is the result of the interaction of an electric and magnetic field because an electric field induces a magnetic field and a magnetic field induces an electric field.
  • An electromagnetic wave can be induced when either the charge of an electric field changes or when the current of a magnetic field changes or when they both change together.
  • The waveform, wavelength and frequency of an electromagnetic wave result from the rapid periodic succession of transitions between the electrical and magnetic components and the forward propagation of the wave through space.
  • When electric and magnetic fields come into contact to form electromagnetic waves they oscillate at right angles to one another.
  • The direction of propagation of an electromagnetic wave is at right angles to the electric and magnetic fields.
  • The velocity at which electromagnetic waves propagate in a vacuum is the speed of light which is 300,000 metres per second.
  • Once an electromagnetic wave propagates outward it cannot be deflected by an external electric or magnetic field.
  • The reason an electromagnetic wave does not need a medium to propagate through is because the only thing that is waving/oscillating is the value of the electric and magnetic fields.

Magnetic field

A magnetic field is created when electric current flows. The greater the current the stronger the magnetic field.

  • Whilst an electric field is created by a change in voltage (charge), a magnetic field is created when electric current flows. The greater the current the stronger the magnetic field.
  • An electromagnetic wave is the result of the interaction of an electric and magnetic field because an electric field induces a magnetic field and a magnetic field induces an electric field.
  • An electromagnetic wave can be induced when either the charge of an electric field changes or when the current of a magnetic field changes or when they both change together.
  • The waveform, wavelength and frequency of an electromagnetic wave result from the rapid periodic succession of transitions between the electrical and magnetic components and the forward propagation of the wave through space.
  • When electric and magnetic fields come into contact to form electromagnetic waves they oscillate at right angles to one another.
  • The direction of propagation of an electromagnetic wave is at right angles to the electric and magnetic fields.

Mass

Mass is the amount of matter in an object and is measured in kilograms (kg).

  • A large object made of a given material has greater mass than a small object made of the same material because it contains less matter.
  • Mass is not the same as weight because an object of a known mass will weigh more on earth than on the moon.
  • An object of a known mass is weightless in free fall.
  • Weight is the force of gravity on an object and is measured in newtons (N).

https://en.wikipedia.org/wiki/Mass

https://en.wikipedia.org/wiki/Newton_(unit)

Material

Material is the matter from which a thing is or can be made.

  • Material is a broad term for a chemical substance or mixture of substances that constitute a thing.
  • Materials can be classified based on different properties such as physical and chemical properties such as geological, biological or philosophical properties.
  • In the physical sense, materials are studied in the field of materials science.

Material thing

A material thing is something formed or consisting of matter.

  • Things are usually objects.
  • An attribute of an object is called a property if it can be experienced (e.g. its colour, size, weight, smell, taste, and location).
  • Objects manifest themselves through their properties.
  • These manifestations seem to change in a regular and unified way, suggesting that something underlies the properties.

Medium

Any material through which an electromagnetic wave propagates (travels) is called a medium (plural media).

  • In optics, a medium is a material through which electromagnetic waves propagate.
  • Although electromagnetic radiation is able to propagate through a wide range of media, it is not dependent upon on any medium for propagation and travels at the speed of light through a vacuum.
  • The reason an electromagnetic wave does not need a medium to propagate through is because the only thing that is waving/oscillating is the value of the electric and magnetic fields.
  • In general terms, empty space (a vacuum) is not considered to be a medium because it does not contain matter.
  • It is the permittivity and permeability of a medium that determines how waves travel.

Medium

Any material through which an electromagnetic wave propagates (travels) is called a medium (plural media).

  • In optics, a medium is a material through which electromagnetic waves propagate.
  • Although electromagnetic radiation is able to propagate through a wide range of media, it is not dependent upon on any medium for propagation and travels at the speed of light through a vacuum.
  • The reason an electromagnetic wave does not need a medium to propagate through is because the only thing that is waving/oscillating is the value of the electric and magnetic fields.
  • In general terms, empty space (a vacuum) is not considered to be a medium because it does not contain matter.
  • It is the permittivity and permeability of a medium that determines how waves travel.

Media

Media is the plural of medium. A medium is any material through which an electromagnetic wave propagates (travels).

  • In optics, a medium is a material through which electromagnetic waves propagate.
  • Although electromagnetic radiation is able to propagate through a wide range of media, it is not dependent upon on any medium for propagation and travels at the speed of light through a vacuum.
  • The reason an electromagnetic wave does not need a medium to propagate through is because the only thing that is waving/oscillating is the value of the electric and magnetic fields.
  • In general terms, empty space (a vacuum) is not considered to be a medium because it does not contain matter.
  • It is the permittivity and permeability of a medium that determines how waves travel.

Matter

Matter is anything that has mass and energy and occupies space by having volume.

  • Matter describes the physical things around us – earth, air and any object that can be named.
  • Matter is made up of particles – atoms and molecules.
  • Subatomic and atomic particles have mass and energy.
  • Light is a form of energy, not matter.
  • Einstein’s equation E=MC2 suggests that anything having mass has an equivalent amount of energy and vice versa.

Metameric

Visually indistinguishable colour stimuli are described as being metameric.

  • Metameric stimuli are colour stimuli that are indistinguishable from one another because they evoke the same response by the three cone cell types on which human vision colour vision depends.
  • A class of metameric stimuli can be specified by a set of tristimulus values, defined as the “amounts of the 3 reference colour stimuli, in a given trichromatic system, required to match the colour of the stimulus considered”.
  • Perhaps the most important application of metameric stimuli is to be found in the use of tristimulus values used in additive colour systems.
  • The RGB colour model, for example, uses mixtures of red, green and blue light to produce the impression of a complete range of colours for an observer.

https://en.wikipedia.org/wiki/Metamerism_(color)

(CIE, 2011, 17-1345)

Müller cell

Definition

Explanation

Müller glia, or Müller cells, are a type of retinal glial cells in the human eye that serve as support cells for the neurons, as other glial cells do.

An important role of Müller cells is to funnel light to the rod and cone photoreceptors from the outer surface of the retina to where the photoreceptors are located.

Other functions include maintaining the structural and functional stability of retinal cells. They regulate the extracellular environment, remove debris, provide electrical insulation of receptors and other neurons, and mechanical support of the neural retina.

  • All glial cells (or simply glia), are non-neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system.
  • Müller cells are the most common type of glial cell found in the retina. While their cell bodies are located in the inner nuclear layer of the retina, they span the entire retina.

https://en.wikipedia.org/wiki/Muller_glia

Nature

Nature is the natural, physical and living world.

  • Nature in the broadest sense, is all of planet Earth, our solar system and the universe beyond.
  • In a more limited sense whilst everything around us is evidence of nature, from the global phenomena of oceans, continents and climate, nature is a carpet of interconnected life forms composed of individual plants, insects and animals.
  • Although humans are part of nature, human activity and the human world with its cities, agriculture and industries are sometimes understood as a separate category from other natural phenomena.
  • The study of nature is a large part of the histories of science and art.

https://en.wikipedia.org/wiki/Nature

Normal

If one line is normal to another, then it is at right angles. So in geometry, the normal is a line drawn perpendicular to and intersecting another line.

In optics, the normal is an imaginary line drawn on a ray diagram perpendicular to, so at a right angle to (900), to the boundary between two media.

  • Light travels in a straight line through a vacuum or a transparent medium such as air, glass, or still water.
  • If light encounters a force, an obstacle or interacts with an object, a variety of optical phenomena may take place including absorption, dispersion, diffraction, polarization, reflection, refraction, scattering or transmission.
  • Optics treats light as a collection of rays that travel in straight lines and calculates the way in which they change direction (deviate) when encountering different optical phenomena.
  • When the normal is drawn on a ray diagram, it provides a reference against which the amount of deviation of the ray can be shown.
  • The normal is always drawn at right angles to a ray of incident light at the point where it arrives at the boundary with a transparent medium.

https://en.wikipedia.org/wiki/Geometrical_optics

Normal

If one line is normal to another, then it is at right angles. So in geometry, the normal is a line drawn perpendicular to and intersecting another line.

In optics, the normal is an imaginary line drawn on a ray diagram perpendicular to, so at a right angle to (900), to the boundary between two media.

  • Light travels in a straight line through a vacuum or a transparent medium such as air, glass, or still water.
  • If light encounters a force, an obstacle or interacts with an object, a variety of optical phenomena may take place including absorption, dispersion, diffraction, polarization, reflection, refraction, scattering or transmission.
  • Optics treats light as a collection of rays that travel in straight lines and calculates the way in which they change direction (deviate) when encountering different optical phenomena.
  • When the normal is drawn on a ray diagram, it provides a reference against which the amount of deviation of the ray can be shown.
  • The normal is always drawn at right angles to a ray of incident light at the point where it arrives at the boundary with a transparent medium.

https://en.wikipedia.org/wiki/Geometrical_optics

Object

An object is a material thing that can be seen and touched.

  • An object is intuitively assumed to exist and to be responsible for a unified experience, consisting of visual and other sensations and perceptions.
  • Every object, material, medium or substance that we can see is made of matter of one kind or another. The key differentiating factor is the elements and molecules they are constructed from.
  • You will have come across the elements that make up the periodic table.
  • A close look at molecules reveals that they are made up of atoms composed of electrons surrounding a nucleus of protons and electrons.
  • Light illuminates objects. In a nutshell, different elements and molecules react to light in different ways because of their atomic structure and the particular way they combine to form mixtures or compounds.
  • In the case of an opaque object, it is the molecules that form its surface that determine what happens when light strikes it. Translucent and transparent objects behave differently because light can travel through them.
  • Another factor that needs to be taken into account when light strikes an object is surface finish. A smooth and polished surface behaves differently from one that is rough, textured or covered in ripples.

Object

An object is a material thing that can be seen and touched.

  • An object is intuitively assumed to exist and to be responsible for a unified experience, consisting of visual and other sensations and perceptions.
  • Every object, material, medium or substance that we can see is made of matter of one kind or another. The key differentiating factor is the elements and molecules they are constructed from.
  • You will have come across the elements that make up the periodic table.
  • A close look at molecules reveals that they are made up of atoms composed of electrons surrounding a nucleus of protons and electrons.
  • Light illuminates objects. In a nutshell, different elements and molecules react to light in different ways because of their atomic structure and the particular way they combine to form mixtures or compounds.
  • In the case of an opaque object, it is the molecules that form its surface that determine what happens when light strikes it. Translucent and transparent objects behave differently because light can travel through them.
  • Another factor that needs to be taken into account when light strikes an object is surface finish. A smooth and polished surface behaves differently from one that is rough, textured or covered in ripples.

Observer

A human observer is a person who engages in observation or watches something.

  • In the presence of light, an observer perceives colour.
  • Things appear coloured to an observer because colour corresponds with a property of light that is visible to the human eye.
  • The visual experience of colour is associated with words such as red, blue, yellow, etc.
  • The perception of colour is a very subjective experience.
  • One factor that determines the particular colour an observer sees is the colour of nearby objects.
  • Another factor is to do with the well-being of an observer. Health, medications, mood, emotions or fatigue can all affect the eye, vision and perception.
  • A further factor is the environment in which colours are observed, the type of object and colour associations.
  • Two different observers may see colour differently because of life experience including educational, social and cultural factors.
  • The term observer has distinct and different meanings within the fields of special relativity, general relativity, quantum mechanics, thermodynamics and information theory.

https://en.wikipedia.org/wiki/Observer_(physics)#General_relativity

Observer

A human observer is a person who engages in observation or watches something.

  • In the presence of light, an observer perceives colour.
  • Things appear coloured to an observer because colour corresponds with a property of light that is visible to the human eye.
  • The visual experience of colour is associated with words such as red, blue, yellow, etc.
  • The perception of colour is a very subjective experience.
  • One factor that determines the particular colour an observer sees is the colour of nearby objects.
  • Another factor is to do with the well-being of an observer. Health, medications, mood, emotions or fatigue can all affect the eye, vision and perception.
  • A further factor is the environment in which colours are observed, the type of object and colour associations.
  • Two different observers may see colour differently because of life experience including educational, social and cultural factors.
  • The term observer has distinct and different meanings within the fields of special relativity, general relativity, quantum mechanics, thermodynamics and information theory.

Opacity

Opacity refers to the degree to which an object, area or surface obscures objects or space beyond.

  • Different processes can lead to opacity including absorptionreflection, and scattering.
  • An entirely opaque substance transmits no light, and therefore reflects, scatters, or absorbs all of it.
  • When light strikes an interface between two media some light may be reflected, some absorbed, some scattered. The remainder undergoes refraction and is transmitted through the second medium.
  • So, opacity is the measure of impenetrability to electromagnetic radiation, especially visible light by a material.
  • An opaque object is neither transparent (allowing all light to pass through) nor translucent (allowing some light to pass through).
  • Both mirrors and carbon black are opaque.
  • Opacity depends on the wavelengths of the light being considered. For instance, some kinds of glass, while transparent in the visual range, are largely opaque to ultraviolet light.

Optic chiasm

The optic chiasm is the part of the human brain where the optic nerves partially cross. The optic chiasm is located at the bottom of the brain immediately below the hypothalamus.

  • The cross-over of optic nerve fibres at the optic chiasm allows the visual cortex to receive the same hemispheric visual field from both eyes.
  • Superimposing and processing these monocular visual signals allow the visual cortex to generate binocular and stereoscopic vision.
  • For example, the right visual cortex receives the temporal visual field of the left eye, and the nasal visual field of the right eye, which results in the right visual cortex producing a binocular image of the left hemispheric visual field. The net result of optic nerves crossing over at the optic chiasm is for the right cerebral hemisphere to sense and process left hemispheric vision, and for the left cerebral hemisphere to sense and process right hemispheric vision.

https://en.wikipedia.org/wiki/Optic_chiasm

Optic nerve

The optic nerve of the human eye is the cable–like grouping of nerve fibres formed from the axons of ganglion cells that transmit visual information towards the lateral geniculate nucleus.

  • The optic nerve contains around a million fibres that transport continuous stream of data which have been received from rods, cones and the intermediate neuron types, bipolar and amacrine cells.
  • The optic nerve is a parallel communication cable that enables every fibre to represent distinct information about the presence of light in each region of the visual field.

https://en.wikipedia.org/wiki/Optic_nerve

optic radiation

The optic radiation are tracts formed from the axons of neurons located in the lateral geniculate nucleus and lead to areas within the primary visual cortex.

  • There is an optic radiation on each side of the brain. They carry visual information through two divisions called the upper and lower divisions to their corresponding cerebral hemisphere.

https://en.wikipedia.org/wiki/Optic_radiation

optical density

Optical density is a measurement of the degree to which a refractive medium slows the transmission of light.

  • The optical density of a medium is not the same as its physical density.
  • The more optically dense a material is, the slower light travels through the material and so the higher the index of refraction.
  • The less optically dense (rare) a material is, the faster light travels through the material and so the lower the index of refraction.
  • A vacuum has the least density and so the highest speed of light.
  • Optical density accounts for the variation in refractive indices of different media.

https://en.wikipedia.org/wiki/Absorbance

Optical phenomena

Optical phenomena result from the behaviour and properties of light, including its interactions with matter. They include absorption, dispersion, diffraction, polarization, reflection, refraction, scattering and transmission.

  • Optics is the branch of physics which describes the behaviour of visible, ultraviolet, and infrared light.
  • Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.
  • Most optical phenomena can be accounted for using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice.
  • Practical optics is usually done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces.
  • Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be accounted for in geometric optics.
  • Some phenomena depend on the fact that light has both wave-like and particle-like properties. Explanation of these effects requires quantum mechanics.
  • When considering light’s particle-like properties, the light is modelled as a collection of particles called photons.
  • Quantum optics deals with the application of quantum mechanics to optical systems.
  • Practical applications of ray diagrams are found in relation to a variety of technologies and descriptions of how everyday objects work, including mirrors, lenses, telescopes, microscopes, lasers, and fibre optics.

Optical phenomena

Optical phenomena result from the behaviour and properties of light, including its interactions with matter. They include absorption, dispersion, diffraction, polarization, reflection, refraction, scattering and transmission.

  • Optics is the branch of physics which describes the behaviour of visible, ultraviolet, and infrared light.
  • Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.
  • Most optical phenomena can be accounted for using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice.
  • Practical optics is usually done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces.
  • Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be accounted for in geometric optics.
  • Some phenomena depend on the fact that light has both wave-like and particle-like properties. Explanation of these effects requires quantum mechanics.
  • When considering light’s particle-like properties, the light is modelled as a collection of particles called photons.
  • Quantum optics deals with the application of quantum mechanics to optical systems.
  • Practical applications of ray diagrams are found in relation to a variety of technologies and descriptions of how everyday objects work, including mirrors, lenses, telescopes, microscopes, lasers, and fibre optics.

Optics

Optics is the science of light and how it interacts with matter.  The observation and study of optical phenomena offer many clues as to the nature of light.

  • Optics explains how rainbows exist, how light reflects off mirrors, how light refracts through glass or water, and what splits light shining through a prism.
  • In addition to visible light in the standard “spectrum” of red, orange, yellow, green, blue, indigo, and violet, optics also deals with invisible parts of the whole electromagnetic spectrum of which visible light is but a small part.
  • Optics is both a science and an area of engineering. It has been used to make many useful things, including eyeglasses, cameras, telescopes, and microscopes. Many of these things are based on lenses, which focus light and can make images of things that are bigger or smaller than the original.
  • While optics is an old science, new things are still being discovered about it. Scientists have learned how to make light travel through a thin optical fibre made of glass or plastic. Light can go long distances in a fibre. Fibres are used to carry phone calls and the Internet between cities.

Geometrical optics, or ray optics, is a model of optics that describes light propagation in terms of rays. A ray in geometric optics is an abstraction useful for approximating the paths along which light propagates under certain circumstances.

  • The simplifying assumptions of geometrical optics include that light rays:
  • Propagate in straight-line paths as they travel in a homogeneous medium
  • Bend, and in particular circumstances may split in two, at the interface between two dissimilar media
  • Follow curved paths in a medium in which the refractive index changes
  • May be absorbed or reflected.
  • Geometrical optics does not account for certain optical effects such as diffraction and interference. This simplification is useful in practice; it is an excellent approximation when the wavelength is small compared to the size of structures with which the light interacts. The techniques are particularly useful in describing geometrical aspects of imaging, including optical aberrations.

https://simple.wikipedia.org/wiki/Optics

https://en.wikipedia.org/wiki/Geometrical_optics

Oscillation

An oscillation is a periodic motion that repeats itself in a regular cycle. An oscillating movement is always around an equilibrium point or mean value. It is also known as a periodic motion.

https://en.wikipedia.org/wiki/Oscillation

Oscillation

An oscillation is a periodic motion that repeats itself in a regular cycle. An oscillating movement is always around an equilibrium point or mean value. It is also known as a periodic motion.