Glossary
Amplitude
The height of a wave from its midline, which determines the intensity or brightness of light.
Example:
A very bright stage light has a high amplitude, making its illumination more intense than a dim nightlight.
Electromagnetic radiation
Energy that travels through space in the form of waves and particles (photons), encompassing a wide range of wavelengths and frequencies.
Example:
From the radio signals that play your favorite music to the X-rays used in medical imaging, all are forms of electromagnetic radiation.
Electromagnetic spectrum
The entire range of electromagnetic radiation, ordered by wavelength or frequency, from gamma rays to radio waves.
Example:
Our eyes can only perceive a tiny sliver of the vast electromagnetic spectrum, which also includes X-rays and microwaves.
Frequency (ν)
The number of waves that pass a fixed point in a given amount of time, measured in Hertz (Hz) or cycles per second.
Example:
A high-pitched sound wave has a high frequency, meaning many wave cycles pass your ear per second.
Gamma (γ) rays
The shortest wavelength and highest frequency form of electromagnetic radiation, known for their high energy and ionizing properties.
Example:
Medical professionals sometimes use controlled bursts of gamma rays in radiation therapy to target and destroy cancer cells.
Infrared (IR) radiation
Electromagnetic radiation with wavelengths longer than visible light, commonly associated with heat and used in thermal imaging.
Example:
When you feel the warmth from a campfire, you are experiencing infrared radiation being emitted by the burning wood.
Microwaves
Electromagnetic radiation with wavelengths longer than infrared, used in communication and for heating food by causing water molecules to vibrate.
Example:
Your kitchen microwave oven heats up leftovers by causing the water molecules within the food to rapidly rotate and generate thermal energy.
Particle-wave duality
The concept that light (and other quantum entities like electrons) exhibits properties of both particles and waves.
Example:
Understanding particle-wave duality helps explain why light can create interference patterns like waves but also knock electrons off a surface like particles.
Photons
Quantum particles that act as force carriers for electromagnetic energy, often described as tiny packets of light energy.
Example:
When a solar panel converts sunlight into electricity, it's capturing the energy from countless incoming photons.
Radio waves
The longest wavelength and lowest frequency form of electromagnetic radiation, primarily used for transmitting signals over long distances.
Example:
When you tune into your favorite station, your car's antenna is receiving radio waves that carry the audio signal.
Spectroscopy
The scientific study of how radiant energy interacts with matter, often used to analyze the composition or properties of substances.
Example:
Astronomers use spectroscopy to determine the chemical composition of distant stars by analyzing the light they emit.
Speed of light (c)
The constant speed at which all electromagnetic radiation travels in a vacuum, approximately 3.0 x 10^8 meters per second.
Example:
Even though the sun is millions of miles away, its light reaches Earth in about eight minutes because of the incredibly fast speed of light.
Ultraviolet (UV) radiation
Electromagnetic radiation with wavelengths shorter than visible light, known for causing sunburns and being used in sterilization.
Example:
Wearing sunscreen helps protect your skin from harmful ultraviolet radiation from the sun, which can cause damage at a cellular level.
Visible light
A type of electromagnetic radiation that is perceptible to the human eye, forming a small portion of the electromagnetic spectrum.
Example:
When you see a vibrant rainbow after a storm, you are observing the different visible light wavelengths separated by water droplets.
Wavelength (λ)
The length of one complete wave cycle, typically measured from peak to peak, and determines the color of visible light.
Example:
Red light has a longer wavelength than blue light, which is why they appear as different colors in the visible spectrum.
X-rays
A form of electromagnetic radiation with wavelengths shorter than UV light but longer than gamma rays, capable of penetrating soft tissues.
Example:
When you break a bone, doctors use X-rays to get an image of the fracture because they pass through skin and muscle but are absorbed by denser bone.