## 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)

## Monochromatic

A monochromatic colour is a colour that corresponds with a single wavelength of light.

• Monochromatic colours are all the colours (tints, tones, and shades) of a single hue.
• Monochromatic colour schemes are derived from a single base hue and extended using its shades and tints (that is, a hue modified by the adjustment of its brightness).

## MÃ¼ller 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