Electric & Magnetic Properties of Light

Electric & Magnetic Properties of Light

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This diagram shows that an electromagnetic wave (lightwave) results from the interaction of an electric and magnetic field.

  • Electromagnetic waves are produced by the Sun as a result of thermonuclear fusion.
  • The explosive force of thermonuclear fusion is caused by gravity crushing hydrogen atoms until they collapse.
  • The nuclear reaction forces hydrogen atoms to combine into helium atoms and release vast amounts of electrical and magnetic energy.
  • The electrical and magnetic forces form fields which interact with each other to produce a wave pattern that radiates out into space at the speed of light.
  • The electromagnetic waves are of every imaginable size. The smallest (gamma rays) transport the most energy. The largest (radio waves) transport the least.
  • Candles and light bulbs also involve heating materials until they give off light.
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Description

Electric & Magnetic Properties of Light

TRY SOME QUICK QUESTIONS AND ANSWERS TO GET STARTED
What is the angle between an electric and magnetic field in an electromagnetic wave?
The angle between the electric and magnetic field is 90 degrees.
What are the causes of electric and magnetic fields?
An electric field is caused by a change in voltage (charge), a magnetic field is created when electric current flows.
Is an electromagnetic wave the same as a light wave?
Yes! A light wave is another name for an electromagnetic wave.
What does propagate mean?
In the case of light waves, to propagate means to travel through a medium in a particular direction.
What are the two fields that form an electromagnetic wave?
An electromagnetic wave is the result of the interaction of electric and magnetic fields.

About the diagram

About the diagram
  • This diagram shows that an electromagnetic wave (lightwave) results from the interaction of an electric field and a magnetic field.
  • Electromagnetic waves are produced by the Sun as a result of thermonuclear fusion.
  • The explosive force of thermonuclear fusion is caused by gravity crushing hydrogen atoms until they collapse.
  • The nuclear reaction forces hydrogen atoms to combine into helium atoms and release vast amounts of electrical and magnetic energy.
  • The electrical and magnetic forces form fields that interact with each other to produce a wave pattern that radiates out into space at the speed of light.
  • The electromagnetic waves are of every imaginable size. The smallest (gamma rays) transport the most energy. The largest (radio waves) transport the least.
  • Candles and light bulbs also involve heating materials until they give off light.
In the diagram:
  • The magnetic wave is coloured red and yellow and forms the vertical axis.
  • The electrical wave is coloured blue and violet and forms the horizontal axis.
  • The direction of propagation is from left to right.
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Some key terms

Electric field

Electric fields are a property of photons. These dynamic fields, along with corresponding magnetic fields, are responsible for the transmission of electromagnetic energy, such as visible light.

  • Photons are massless particles that carry electromagnetic energy, with each photon representing a quantum of light. The electric fields produced by photons oscillate, meaning their strength varies cyclically between maximum and minimum values over time.
  • The frequency of the electric field determines the frequency of the photon. A higher photon frequency corresponds to a shorter wavelength, as frequency and wavelength are inversely related.
Electromagnetic radiation

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 wave

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.

 

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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.
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.

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