Written by MIRORlab Design Team
Light is the foundation of our visual world, allowing us to perceive colors, shapes, and spaces. But what exactly is light, and how do designers like MIRORlab utilize the science of light to create captivating lighting products? This comprehensive guide explores the physics of light, its visible and invisible forms, and how these principles translate into thoughtful lighting design.
What Is Light?
At its core, light is a form of electromagnetic radiation that travels in waves. These waves propagate through space at approximately 299,792,458 meters per second in a vacuum—a speed so fundamental to physics that it's known simply as "the speed of light."
What makes light fascinating from both scientific and design perspectives is its dual nature: it behaves both as a wave and as a particle (called a photon) simultaneously. This duality allows designers to manipulate light in various ways to create different effects, from precise task lighting to ambient mood illumination.
The electromagnetic spectrum encompasses all possible frequencies of electromagnetic radiation. Light as we typically think of it represents just a small portion of this vast spectrum.
Understanding Visible Light
Visible light is the narrow band of electromagnetic radiation that human eyes can detect, spanning wavelengths from approximately 380 nanometers (violet) to 700 nanometers (red). This tiny slice of the electromagnetic spectrum provides us with the colorful world we experience daily.
The visible spectrum creates the familiar rainbow of colors through dispersion, where white light separates into its constituent colors:
- Violet (380-450 nm)
- Blue (450-495 nm)
- Green (495-570 nm)
- Yellow (570-590 nm)
- Orange (590-620 nm)
- Red (620-700 nm)
Each color corresponds to a specific wavelength and energy level. Violet has the shortest wavelength and highest energy within the visible spectrum, while red has the longest wavelength and lowest energy.
Beyond Visibility: Non-Visible Light
Most electromagnetic radiation falls outside our visual perception but plays crucial roles in both nature and technology:
Ultraviolet (UV) Light
UV radiation has wavelengths shorter than visible light (10-380 nm) and is divided into UVA, UVB, and UVC. While invisible to humans, many insects can see UV light. In lighting design, UV considerations are important for preventing material degradation and ensuring human safety.
Infrared (IR) Light
Infrared light has longer wavelengths than visible light (700 nm to 1 mm) and is experienced as heat. IR is important in lighting design for managing thermal output and energy efficiency.
Other Forms of Electromagnetic Radiation
Beyond UV and IR lie radio waves, microwaves, X-rays, and gamma rays—all forms of electromagnetic radiation that differ only in wavelength and energy.
The Physics of Light: Key Concepts
Understanding several fundamental principles helps explain how light behaves:
Reflection and Refraction
Reflection occurs when light bounces off surfaces, while refraction happens when light passes through different mediums, changing direction. These principles are essential in lens design and light distribution patterns.
Absorption and Transmission
Different materials absorb or transmit various wavelengths of light differently, creating the colors we see. When light strikes an object, certain wavelengths are absorbed while others are reflected back to our eyes.
Diffusion and Scattering
Diffusion spreads light in multiple directions, softening harsh light sources. Scattering occurs when light particles interact with small particles in a medium, changing direction—creating phenomena like blue skies and red sunsets.
Lighting Units and Measurements
Several units help quantify different aspects of light:
Lumens (lm)
Lumens measure the total quantity of visible light emitted by a source. Unlike watts (which measure energy consumption), lumens directly indicate brightness—making them crucial for selecting appropriate lighting intensity for different spaces and applications.
Lux (lx)
Lux measures illuminance—the amount of light that falls on a surface. One lux equals one lumen per square meter. This measurement helps lighting designers ensure adequate light levels for specific tasks and environments.
Candela (cd)
Candela measures luminous intensity in a particular direction. This unit helps understand how light is distributed from a source and is fundamental to designing directional lighting.
Color Temperature (Kelvin)
Color temperature describes the warmth or coolness of light, measured in Kelvin (K). Lower values (2700-3000K) create warm, yellowish light similar to incandescent bulbs, while higher values (5000-6500K) produce cooler, bluish light resembling daylight.
Color Rendering Index (CRI)
CRI measures how accurately a light source reveals the true colors of objects compared to natural light on a scale of 0-100. Higher CRI values (90+) indicate excellent color rendering, essential for applications where color accuracy matters.
Unified Glare Rating (UGR)
UGR measures the discomfort glare produced by lighting installations. Lower values indicate less glare, with ratings below 19 typically recommended for office and educational settings to prevent eye strain and discomfort.