Glossary
Amplitude (of EM waves)
The maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position. For EM waves, it relates to the strength of the electric and magnetic fields.
Example:
A louder sound wave has a greater amplitude, just as a brighter light wave has a greater electric field amplitude.
Electric Fields
Regions around a charged particle or varying magnetic field where a force would be exerted on other charged particles.
Example:
A charged balloon creates an electric field that can attract small pieces of paper.
Electromagnetic (EM) Spectrum
The entire range of all possible frequencies of electromagnetic radiation, categorized by wavelength and frequency.
Example:
From radio waves used in communication to gamma rays used in cancer treatment, the electromagnetic (EM) spectrum encompasses all forms of light.
Electromagnetic Waves
Waves composed of oscillating electric and magnetic fields that propagate through space, even a vacuum, without needing a medium.
Example:
The light from the sun reaching Earth is an example of an electromagnetic wave traveling through the vacuum of space.
Energy (of EM waves/photons)
The capacity of an electromagnetic wave or photon to do work, directly proportional to its frequency.
Example:
High-frequency gamma rays carry significant energy, which is why they can be dangerous but also useful in medical treatments.
Frequency (f)
The number of complete wave cycles that pass a given point per unit of time, measured in Hertz (Hz).
Example:
A radio station broadcasts at a specific frequency, like 98.7 MHz, indicating how many wave cycles per second its signal completes.
Gamma rays
The highest-energy electromagnetic waves with the shortest wavelengths, produced by radioactive decay and nuclear processes.
Example:
Gamma rays are used in radiation therapy to target and destroy cancerous cells due to their high energy.
Infrared
Electromagnetic waves with wavelengths longer than visible light but shorter than microwaves, often associated with heat.
Example:
Night vision goggles detect infrared radiation emitted by warm objects, allowing you to see in the dark.
Intensity (of EM waves)
The power per unit area carried by an electromagnetic wave, related to the square of its amplitude.
Example:
Turning up the brightness on a flashlight increases the intensity of the light beam, making it appear brighter.
Magnetic Fields
Regions around a magnet or a current-carrying conductor where a magnetic force can be detected.
Example:
The Earth's magnetic field protects us from harmful solar radiation.
Microwaves
Electromagnetic waves with shorter wavelengths than radio waves but longer than infrared, commonly used in cooking and radar.
Example:
A microwave oven heats food by causing water molecules to vibrate rapidly.
Photon
A quantum of electromagnetic radiation, a discrete packet of energy that carries light and all other forms of electromagnetic radiation.
Example:
When light hits a solar panel, individual photons transfer their energy to electrons, generating electricity.
ROYGBV
An acronym representing the order of colors in the visible light spectrum from longest wavelength (lowest frequency) to shortest wavelength (highest frequency): Red, Orange, Yellow, Green, Blue, Violet.
Example:
When you see a rainbow, the colors are always arranged in the ROYGBV sequence.
Radio waves
Electromagnetic waves with the longest wavelengths and lowest frequencies, used primarily for communication.
Example:
Your car stereo receives radio waves to play music from distant stations.
Refractive Index (n)
A dimensionless number that describes how fast light travels through a medium, defined as the ratio of the speed of light in a vacuum to its speed in the medium.
Example:
A diamond has a high refractive index, causing light to slow down significantly and bend sharply, creating its sparkle.
Speed of Light (c)
The constant speed at which all electromagnetic waves travel in a vacuum, approximately $3 \times 10^8 m/s$.
Example:
It takes about 8 minutes for light from the sun to reach Earth, traveling at the speed of light (c).
Transverse Waves
Waves in which the oscillations of the medium or field are perpendicular to the direction of energy transfer or wave propagation.
Example:
When you shake a rope up and down to create a wave, the wave travels horizontally while the rope moves vertically, demonstrating a transverse wave.
Ultraviolet
Electromagnetic waves with wavelengths shorter than visible light but longer than X-rays, known for causing sunburns.
Example:
Sunscreen protects your skin from harmful ultraviolet radiation, which can cause skin damage.
Visible light
The narrow portion of the electromagnetic spectrum that is detectable by the human eye, ranging from red to violet.
Example:
A rainbow displays the full spectrum of visible light as white light is dispersed into its constituent colors.
Wavelength (λ)
The spatial period of a periodic wave, which is the distance over which the wave's shape repeats.
Example:
Red light has a longer wavelength than blue light, which is why it scatters less and can travel further through fog.
X-rays
High-energy electromagnetic waves with very short wavelengths, capable of penetrating soft tissues and used in medical imaging.
Example:
Doctors use X-rays to view broken bones because the waves pass through flesh but are absorbed by denser bone.