Electromagnetic Spectrum Vocabulary

Vocabulary flashcards covering the concepts, definitions, equations, names, and applications related to the Electromagnetic Spectrum from the lecture notes.

Electromagnetic Spectrum (EMR)

Transverse waves consisting of radiation energy that travels and spreads out as it goes, carrying energy from one place to another.

Wave speed ($v$)

A wave characteristic typically measured in meters per second ($m/s$).

Wavelength ($\lambda$)

The distance between a crest and the adjacent crest, or a trough and the adjacent trough, representing the length of one complete cycle.

Frequency ($f$)

The number of waves passing through a given point during the interval of $1\,s$, or the number of complete vibrations per second of the field at a point.

Heinrich Rudolf Hertz

German physicist ($1857-1894$) credited with the unit of frequency.

Hertz ($\text{Hz}$)

The unit of measurement for frequency, defined as cycles per second.

Kilohertz ($\text{kHz}$)

A unit of frequency equal to $10^3$ or $1,000$ cycles per second.

Megahertz ($\text{MHz}$)

A unit of frequency equal to $10^6$ or $1\text{ million}$ cycles per second.

Longitudinal wave wavelength

The distance measured from a compression to the next compression or from a rarefaction to the next rarefaction.

Speed of light ($c$)

The wave speed of all electromagnetic waves in a vacuum, equal to $3.0 \times 10^8\,m/s$.

Period ($T$)

The amount of time required to complete one full cycle of the wave, calculated as $T = 1/f$ or $T = \lambda/v$.

Crest

The highest point of a wave.

Trough

The lowest point of a wave.

Amplitude ($A$)

The maximum distance moved by a particle from its resting position, where greater amplitude indicates a greater amount of energy.

Transverse waves

Waves where the oscillating electric and magnetic fields are perpendicular to the direction in which the waves move.

Photon

A bundle of energy contained within each particle of electromagnetic radiation.

Radio waves

The electromagnetic waves with the longest wavelength in the electromagnetic spectrum, used to transmit radio and television signals.

Standard AM broadcast band

Radio waves with longer wavelengths ranging from $180\,m$ to $550\,m$ and frequencies from $5.4 \times 10^5\,\text{Hz}$ to $1.7 \times 10^6\,\text{Hz}$.

Radio Frequency (RF)

A rate of oscillation in the range of about $3\,\text{kHz}$ to $300\,\text{GHz}$, corresponding to the frequency of radio waves and alternating currents carrying radio signals.

Wireless telegraphy

A historical term for early radio telegraph communication techniques and practices used during the first three decades of radio.

Samuel Thomas Sommering

Creator of an electrochemical telegraph in $1809$, representing one of the early experiments in electrical telegraphy.

Sir Charles Wheatstone and Sir William Fothergill Cook

Constructors of the first commercial electrical telegraph in England.

Samuel Morse

Developer of a version of electrical telegraph technology on the American side of the Atlantic Ocean.

James Clerk Maxwell

Physicist who showed mathematically that electromagnetic waves could propagate through free space.

Nikolas Tesla

Experimented on the transmission and radiation of radio frequency energy and proposed it for telecommunication of information.

Alexander Graham Bell

Inventor who patented the conventional telephone in $1876$.

James Lindsay

Demonstrated wireless telegraphy within a two-mile distance using water as a transmission medium in $1854$.

Slaby-Arco Wireless system

A wireless system developed around the turn of the century by Adolf Slaby and Georg von Arco.

Reginald Fessenden

Pioneer who made a weak transmission of voice over the airwaves in $1900$.

Guglielmo Marconi

First to demonstrate the application of radio in commercial, military, and marine communications and founder of a radio development company.

John Logie Baird

Scottish inventor who obtained moving pictures with halftone shades in October $1925$ using a device known as mechanical television.

Mechanical television

Device developed by John Logie Baird that was the basis of semi-experimental broadcasts by the British Broadcasting Corporation starting September $30$, $1929$.

Microwaves

Extremely high-frequency radio waves with very short wavelengths ranging from approximately $1\,\text{mm}$ to $30\,\text{cm}$.

Sir William Hershel

Discoverer who proved the existence of infrared in $1800$ by passing sunlight through a prism.

Infrared radiation

Electromagnetic radiation with a wavelength longer than visible light, measured from $0.7\,\mu\text{m}$ to $300\,\mu\text{m}$.

Near infrared light

Infrared light closest in wavelength to visible light, used in devices such as a television remote control.

Far infrared light

Infrared light closer to the microwave region of the EM spectrum, experienced as heat from sources like sunlight, fire, or a radiator.

Visible light

The portion of electromagnetic radiation visible to the human eye, with red having the longest wavelength and violet having the shortest.

Ultraviolet radiation

Electromagnetic radiation with wavelengths shorter than visible light but longer than X-rays, having frequencies higher than violet light.

X-rays

High-energy waves with great penetrating power used in medical applications and weld inspection; also called Röntgen radiation.

Wilhelm Conrad Röntgen

Physicist who named X-radiation in $1895$ to signify an unknown type of radiation.

Gamma rays

Radiation generated by radioactive atoms and nuclear explosions, utilized in medical applications.

Gamma-knife surgery

A medical procedure directing multiple concentrated beams of gamma rays on a growth to kill cancerous cells.

Stochastic effects

Radiation effects associated with long-term, low-level exposure to radiation.

Non-stochastic effects

Radiation effects that appear in cases of exposure to high levels of radiation and become more severe as exposure increases.

External beam therapy

A form of radiation therapy that uses radiation produced outside the body focused on cancer cells inside the body.

Brachytherapy

A form of radiation therapy involving placement of radioactive substances in or on the surface of the body near cancer cells.

Systemic radiation therapy

A form of radiation therapy involving swallowing or injecting radioactive isotopes that travel through the bloodstream to cancer cells.