What Is White Light and How Does It Vary?

White light is the light that humans perceive as white, a combination of all visible wavelengths of the electromagnetic spectrum. Let’s take a look at how this works and how we can work with it considering how it’s perceived by our eyes.

What is White Light?

So white light is a type of visible light that is composed of a combination of wavelengths from the electromagnetic spectrum, which is the range of all types of electromagnetic radiation.

White light has no single wavelength, but is a combination of all different wavelengths on the visible spectrum. It is the sun that produces white light, but white light can also be seen in nature in certain phenomena like snow, and from artificial lighting sources.

The visible spectrum is the portion of the electromagnetic spectrum that humans can see. It falls between 400 nanometers and 700 nanometers, with nanometers representing one billionth of a meter. The visible spectrum is divided into the seven distinct colors found in the rainbow, namely red, orange, yellow, green, blue, indigo and violet (ROYGBIV).

White white light is composed of all these colors combined, each color on the visible spectrum has its own unique wavelength. Differentiations within this mix of colors will result in a different type of white light.

Understanding the Electromagnetic Spectrum

The electromagnetic spectrum is a range of frequencies of energy, including radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.

In order to truly understand white light, it is important to understand the electromagnetic spectrum.

This spectrum is often referred to as the rainbow of light, as it contains a range of visible colors from red to violet. When white light passes through a prism, it splits into these component colors because each color of visible light has a different wavelength and is refracted by the prism at a different angle.

The light that we see as white light is actually just a small part of the electromagnetic spectrum. The portion of the spectrum that humans can see with their eyes is called the human visible spectrum or ‘light’.

Sources of White Light

The sun is the primary source of white light for the earth. Sunlight is a combination of all the different colors on the visible spectrum and this is what we see as white light. The sun produces not only a wide range of visible colors, but also invisible infrared and ultraviolet radiation.

White light can also be artificially created with the help of a light source, typically one of the many formats of LED lighting. Until LED was the dominant choice, a traditional incandescant light bulb worked by passing electricity through a wire, which causes the wire to heat up and glow. This produced light in a combination of all the different colors on the visible spectrum, and is what we saw as white light.

Why White Light Ranges in Shades

So white light can range in shades depending on a variety of factors.

Color Temperature

One factor is the temperature of the light source.

The color temperature of white light is another important factor that can affect its shade. Color temperature is a measure of the warmth or coolness of the light source and is measured in degrees Kelvin (K). Lower color temperatures (from around 1800K) produce a rich warm white light, while higher color temperatures (4000K) produce a cool white light and 5500K and above produce an increasingly bluer daylight.

For example found in nature is sunlight, as it is white but it can range from a warm yellow-white to a cool blue-white depending on the time of day and the season.

Wavelength Mixes

White light can appear in different shades due to the fact that different sources of white light have different mixes of the fundemental ‘ROYGBIV’ colors. Sunlight, for example, is generally perceived as a warm white due to the fact that the sun emits more red, orange and yellow wavelengths than blue and indigo wavelengths.

Light Source Composition

Another factor is the composition of the light source. Incandescent bulbs produce a warm white light of 2700K, while LED lights can be designed to produce different shades of white by varying the composition of the materials used in the bulb.

LED lighting uses a varying recipe of a phosphor coating to create a wide variety of shades of white light.

Surrounding Environment

The environment in which the light is viewed can also affect its appearance due to reflectance. White light will collect a characteristic of the surface from which it is reflected from.

For example, a green wall will reflect and appear to change the shade of white light that is shone on it.

Perception of White Light

The human eye is capable of perceiving a wide range of shades of white light, and this ability is important in many aspects of our daily lives.

For example, in interior design and lighting, choosing the right shade of white can help create a specific atmosphere or mood.

In photography and film, adjusting the color temperature of the lighting can be used to create different effects and moods.

As the human eye is capable of distinguishing between different shades of the fundemental ROYGBIV colors, it allows us to perceive different shades of white light. The perception of color can be influenced by factors such as the lighting conditions, the surrounding colors, and individual differences in color perception.

It is also important to note that the perception of color is a complex process that involves the interaction between the eyes, the brain, and the environment. While the human eye can perceive a wide range of colors and shades of white light, the exact number of colors that we can perceive is difficult to quantify.

Andrew Orange, the owner of Orange Lighting qualified and worked as an interior designer in 1993 before specialising in lighting working on high profile projects based in London. Since starting Orange Lighting Ltd in 2003 he has been sharing his knowledge and unique teaching style mostly to his designer clients, offering practical real life advice born from running a busy consultancy and lighting supply business. Launching in 2020, his blog has evolved into Quick & Easy Lighting, curating some 25 years design experience into making the lighting choice and design process achievable and easy to understand for all.