## Electric and magnetic fields

An electric field is created by a change in voltage (charge). The higher the voltage the stronger the field.

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

• A change in an electric field induces a change in the magnetic field.
• A change in a magnetic field induces a change in the electric field.
• An electromagnetic wave is the result of the interaction of electric and magnetic fields.
• An electromagnetic wave can be propagated when either the charge of an electric field changes or when the current of a magnetic field changes.
• When changes in electric and magnetic fields result in electromagnetic waves, they produce synchronised oscillations that travel at right angles to one another.
• The velocity at which electromagnetic waves propagate in a vacuum is the speed of light which is 300,000 kilometres 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.

An electric field is created by a change in voltage (charge). The higher the voltage the stronger the field.

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

• A change in an electric field induces a change in the magnetic field.
• A change in a magnetic field induces a change in the electric field.
• An electromagnetic wave is the result of the interaction of electric and magnetic fields.
• An electromagnetic wave can be propagated when either the charge of an electric field changes or when the current of a magnetic field changes.
• Once an electromagnetic wave propagates outward it cannot be deflected by an external electric or magnetic field.

###### References
• https://en.wikipedia.org/wiki/Electric_field
• https://en.wikipedia.org/wiki/Magnetic_field
• https://en.wikipedia.org/wiki/Electromagnetic_field

## Electric and magnetic fields

An electric field is created by a change in voltage (charge). The higher the voltage the stronger the field.

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

• A change in an electric field induces a change in the magnetic field.
• A change in a magnetic field induces a change in the electric field.
• An electromagnetic wave is the result of the interaction of electric and magnetic fields.
• An electromagnetic wave can be propagated when either the charge of an electric field changes or when the current of a magnetic field changes.
• Once an electromagnetic wave propagates outward it cannot be deflected by an external electric or magnetic field.

## Electric field

An electric field is created by a change in voltage (charge). The higher the voltage the stronger the 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.
• 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 that the only thing that is waving/oscillating is the value of the electric and magnetic fields.

## Electric field

An electric field is caused by a change in voltage (charge). The higher the voltage the stronger the field.

• Whilst an electric field is caused by a change in voltage (charge), a magnetic field is caused 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 a right angle 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 that the only thing that is waving/oscillating is the value of the electric and magnetic fields.

An electric field is created by a change in voltage (charge). The higher the voltage the stronger the 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.
• 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 that the only thing that is waving/oscillating is the value of the electric and magnetic fields.
###### About electric charge
• Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field.
• An electric charge can be positive or negative (commonly carried by protons and electrons respectively).
• Like charges repel each other and unlike charges attract each other.
• An object with an absence of net charge is referred to as neutral.
• If two objects with the same charge are brought towards each other the force produced will be repulsive and it will push them apart.
• If two objects with opposite charges are brought towards each other the force will be attractive and it will pull them towards each other.

## Electromagnetic energy

Electromagnetic energy (electromagnetic radiant energy) is the term used when the energy being transported by electromagnetic waves undergoes measurement.

Electromagnetic energy can also be described as energy transported by particles (called photons) rather than waves in which case electromagnetic radiant energy is measured in terms of photon energy.

• Electromagnetic radiation is also called EM radiation, EMR and electromagnetic radiant energy.
• Stars including the sun radiate electromagnetic energy through space at every wavelength of the electromagnetic spectrum.
• When the waveform of electromagnetic radiation is being considered, electromagnetic energy is measured by calculating the frequency of the electromagnetic waves.
• The unit used to calculate frequency is the hertz (Hz). One hertz equals one wave-cycle per second.
• When electromagnetic radiation is being considered in terms of photons, the elementary particles of the electromagnetic field, then the higher the photon’s frequency, the higher its energy and the longer the photon’s wavelength, the lower its energy.
• Photon energy is solely a function of the photon’s wavelength and frequency.
• Other factors, such as the intensity of the radiation, do not affect photon energy. In other words, two photons of light with the same colour and therefore, same frequency, will have the same photon energy, even if one was emitted from a wax candle and the other from the Sun.
• Units of energy commonly used to denote photon energy are the electronvolt (eV) and the joule. Whilst power is measured in joules per second.

Summary

## Electromagnetic field

An electromagnetic field can be thought of as a single more complete object than its component electric and magnetic field. It propagates through space in the form of bundles of energy called photons which are configured as electromagnetic waves, the force carriers of radiant energy (electromagnetic radiation).

## Electromagnetic field

An electromagnetic field can be thought of as a single more complete object than its component electric and magnetic fields. An electromagnetic field propagates through space in the form of bundles of energy called photons which are configured as electromagnetic waves, the force carriers of radiant energy (electromagnetic radiation).

An electromagnetic field can be thought of as a single more complete object than its component electric and magnetic field. It propagates through space in the form of bundles of energy called photons which are configured as electromagnetic waves, the force carriers of radiant energy (electromagnetic radiation).

• An electromagnetic field results from the coupling of an electric and magnetic field.
• When an electromagnetic field experiences a change in voltage or current its reconfiguration into an electromagnetic wave can be described in terms of wavelength, frequency and energy.
• An electromagnetic wave can be thought to come into existence when a static electric field experiences a change in voltage or a static magnetic field experiences a change in current producing radiating oscillations of electromagnetic energy that propagate through space.
• The difference between an electromagnetic field and an electromagnetic wave is that the wave has a non-zero frequency component which is the source of the energy it transports.
• Electromagnetic radiation is essentially the result of an oscillating electromagnetic field propagating through space.

## Electromagnetic force

The electromagnetic force is one of the four fundamental interactions (commonly called fundamental forces) in nature.

• The electromagnetic force occurs between electrically charged particles.
• The electromagnetic force is carried by the photon and creates electric and magnetic fields, which are responsible for electromagnetic waves (including visible light) and chemical bonding.
• The electromagnetic force forms the basis for all forms of technology involving electricity.

Summary

###### References

Electromagnetic radiation is a type of energy more commonly simply called light. Detached from its source, it is transported by electromagnetic waves (or their quanta, photons) and propagates through space at the speed of light.

• Electromagnetic radiation (EM radiation or EMR) includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.
• Man-made technologies that produce electromagnetic radiation include radio and TV transmitters, radar, MRI scanners, microwave ovens, computer screens, mobile phones, all types of lights and lamps, electric blankets, electric bar heaters, lasers and x-ray machines.
• At the quantum scale of electromagnetism, electromagnetic radiation is described in terms of photons rather than waves. Photons are elementary particles responsible for all electromagnetic phenomena.
• The term quantum refers to the smallest quantity into which something can be divided. A quantum of a thing is indivisible into smaller units so they have no sub-structure.  A photon is a quantum of electromagnetic radiation.
• A single photon with a wavelength corresponding with gamma rays might carry 100,000 times the energy of a single photon of visible light.

Electromagnetic radiation is a type of energy more commonly simply called light. Detached from its source, it is transported by electromagnetic waves (or their quanta, photons) and propagates through empty space at the speed of light.

• Electromagnetic radiation (EM radiation or EMR) includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.
• Man-made technologies that produce electromagnetic radiation include radio and TV transmitters, radar, MRI scanners, microwave ovens, computer screens, mobile phones, all types of lights and lamps, electric blankets, electric bar heaters, lasers and x-ray machines.
• At the quantum scale of electromagnetism, electromagnetic radiation is described in terms of photons rather than waves. Photons are elementary particles responsible for all electromagnetic phenomena.
• The term quantum refers to the smallest quantity into which something can be divided. A quantum of a thing is indivisible into smaller units so they have no sub-structure.  A photon is a quantum of electromagnetic radiation.
• A single photon with a wavelength corresponding with gamma rays might carry 100,000 times the energy of a single photon of visible light.

Electromagnetic radiation is a type of energy more commonly simply called light. Detached from its source, it is transported by electromagnetic waves (or their quanta, photons) and propagates through space at the speed of light.

• Electromagnetic radiation (EM radiation or EMR) includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.
• Man-made technologies that produce electromagnetic radiation include radio and TV transmitters, radar, MRI scanners, microwave ovens, computer screens, mobile phones, all types of lights and lamps, electric blankets, electric bar heaters, lasers and x-ray machines.
• At the quantum scale of electromagnetism, electromagnetic radiation is described in terms of photons rather than waves. Photons are elementary particles responsible for all electromagnetic phenomena.
• The term quantum refers to the smallest quantity into which something can be divided. A quantum of a thing is indivisible into smaller units so they have no sub-structure.  A photon is a quantum of electromagnetic radiation.
• A single photon with a wavelength corresponding with gamma rays might carry 100,000 times the energy of a single photon of visible light.

## Electromagnetic spectrum

The electromagnetic spectrum includes electromagnetic waves with all possible wavelengths of electromagnetic radiation, ranging from low energy radio waves through visible light to high energy gamma rays.

## Electromagnetic spectrum

The electromagnetic spectrum includes electromagnetic waves with all possible wavelengths (and corresponding frequencies) of electromagnetic radiation, ranging from low energy radio waves through visible light to high energy gamma rays.

The electromagnetic spectrum includes electromagnetic waves with all possible wavelengths of electromagnetic radiation, ranging from low energy radio waves through visible light to high energy gamma rays.

• There are no precisely defined boundaries between the bands of electromagnetic radiation in the electromagnetic spectrum.
• The electromagnetic spectrum includes, in order of increasing frequency and decreasing wavelength: radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
• Visible light is only a very small part of the electromagnetic spectrum.

## Electromagnetic wave

Electromagnetic waves are composed of oscillating magnetic and electric fields. So all forms of light within the electromagnetic spectrum can be thought of as vibrations produced as a result of the interaction between an electric field and a magnetic field.

• Electromagnetic waves carry electromagnetic radiant energy.
• The energy carried by electromagnetic waves is often simply called radiant energy or light.
• We can feel electromagnetic waves release their energy when sunlight warms our skin.
• The amount of energy they carry is related to their frequency and their amplitude. The higher the frequency, the more energy, and the higher the amplitude, the more energy.
• The three principal properties of an electromagnetic wave are:
• Velocity (v): The measure of how fast and in what direction a wave propagates in a given medium.
• Wavelength (λ): The distance over which the shape of a wave repeats. Wavelength is measured in meters or its sub-units.
• Frequency (f): Frequency is measured in cycles per second. The unit of frequency is Hertz or its sub-units.
• Each of these three quantities for describing EM radiation are related to one another in a precise mathematical way.
• The position of an electromagnetic wave in the electromagnetic spectrum can be characterized by either its frequency of oscillation or wavelength.
• The electromagnetic spectrum includes, in order of increasing frequency and decreasing wavelength: radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
###### About the properties of photons
• A photon is a single indivisible bundle (particle or wave) of energy within an electromagnetic field.
• A photon is an elementary particle and represents a quantum (plural =quanta) of light – the smallest quantity into which light can be divided.
• Whilst the field of optics often explains light in terms of waves, this description doesn’t always fit the evidence.
• Light sometimes exhibits wave-like behaviour, at others, it behaves like both waves and particles or just as particles.

Other properties of photons include:

• They have zero mass and rest energy. They only exist as moving particles.
• They are elementary particles despite lacking rest mass.
• They have no electric charge.
• They are stable.
• They carry energy and momentum which are dependent on the frequency.
• They can have interactions with other particles such as electrons.
• They can be destroyed or created by many natural processes, for instance when radiation is absorbed or emitted.
• When in empty space, they travel at the speed of light.
###### References

An electromagnetic wave carries electromagnetic radiation.

• An electromagnetic wave is formed as electromagnetic radiation propagates from a light source, travels through space and encounters different materials.
• Electromagnetic waves can be imagined as synchronised oscillations of electric and magnetic fields that propagate at the speed of light in a vacuum.
• Electromagnetic waves are similar to other types of waves in so far as they can be measured in terms of wavelength, frequency and amplitude.
• We can feel electromagnetic waves release their energy when sunlight warms our skin.
• Remember that electromagnetic radiation can be described either as an oscillating wave or as a stream of particles, called photons, which also travel in a wave-like pattern.
• The notion of waves is often used to describe phenomena such as refraction or reflection whilst the particle analogy is used when dealing with phenomena such as diffraction and interference.

## Electromagnetic waves

The form and composition of rainbows are often explained in terms of electromagnetic waves. Electromagnetic waves consist of coupled oscillating electric and magnetic fields orientated at 900 to one another. (Credit: https://creativecommons.org/licenses/by-sa/4.0)

• Electromagnetic waves can be imagined as oscillating electric (E) and magnetic (B) fields arranged at right angles to each other.
• In the diagram above, the coupled electric and magnetic fields follow the y-axis and z-axis and propagate along the x-axis.
• This arrangement is known as a transverse wave which means the oscillations are perpendicular to the direction of travel.
• By convention, the electric field is shown in diagrams aligned with the vertical plane and the magnetic field with the horizontal plane.
• In normal atmospheric conditions the geometric orientation of the coupled y-axis and z axis is random, so the coupled fields EB may be rotated to any angle.

## Electromagnetism

Electromagnetism is a branch of physics involving the study of the electromagnetic force which is one of the four fundamental forces in nature.

• The four fundamental forces (fundamental interactions) are:
• The electromagnetic force
• The strong interaction
• The weak interaction
• Gravity.

Summary

## Electronvolt

An electronvolt is a unit of energy commonly used to measure the energy carried by electromagnetic radiation.

• Electronvolts can be used for measurements at the scale of elementary particles as small as single photons, the quantum of the electromagnetic field.
• One electronvolt is the amount of energy that a single electron has when it is accelerated by a potential difference of 1 volt.
• If there is a difference in voltage of 1 volt between two points in an electrical circuit (within a capacitor for example) then the force required (and the energy gained) by a photon accelerating from one point to the other is 1 electronvolt.

## Electronvolt

An electronvolt is a unit of energy commonly used to measure the energy carried by electromagnetic radiation.

• Electronvolts can be used for measurements at the scale of elementary particles as small as single photons, the quantum of the electromagnetic field.
• One electronvolt is the amount of energy that a single electron has when it is accelerated by a potential difference of 1 volt.
• If there is a difference in voltage of 1 volt between two points in an electrical circuit (within a capacitor for example) then the force required (and the energy gained) by a photon accelerating from one point to the other is 1 electronvolt.
• The electronvolt is not an SI unit of measurement.
• The joule, which is an SI unit of measurement, is too big to use at the level of particle physics.
• 1,000,000,000,000,000,000 eV = 0.1602176565 joule.
• The electronvolt is commonly used with metric prefixes.

An electronvolt is a unit of energy commonly used to measure the energy carried by electromagnetic radiation.

• Electronvolts can be used for measurements at the scale of elementary particles as small as single photons, the quantum of the electromagnetic field.
• One electronvolt is the amount of energy that a single electron has when it is accelerated by a potential difference of 1 volt.
• If there is a difference in voltage of 1 volt between two points in an electrical circuit (within a capacitor for example) then the force required (and the energy gained) by a photon accelerating from one point to the other is 1 electronvolt.

## Element

An element is a substance made from only one type of atom.

• Every element contains a different type of atom.
• The difference between the atoms of different elements is the number of protons present in the nucleus.
• Unlike a compound, the chemical structure of an element cannot be broken down into a more simple substance.
• A complete list of elements can be found in the Periodic Table which orders each element according to its atomic number.
• Atomic numbers correspond with the number of protons present in each nucleus.

Summary

## Emission

When an element or compound is heated it emits electromagnetic radiation of different wavelengths.

• The Sun emits the full spectrum of electromagnetic radiation including all wavelengths of light from low energy radio waves to very high energy gamma rays.
• Artificial light sources, including lamps of all kinds, typically emit more limited bands of wavelengths of visible light.
• When looking directly at a light source, its colour corresponds with the wavelengths being transmitted.
• Display devices such as computer screens emit wavelengths corresponding to red, green and blue primary colours. These are combined in different proportions to produce as many as 16 million colours.
• Printing relies on the reflection of light off a white surface such as a sheet of paper. The surface is overlaid with inks. Transparent inks allow light to pass through to the paper where it is reflected back. The colour of the ink determines which wavelengths pass through the ink after reflection and so which colours an observer sees.
• When light strikes opaque inks some wavelengths are absorbed and some are reflected off the surface.

Summary