You’ve no doubt heard of light being referred to as warm or cold but may not realize that the color of light is often measured in degrees of heat. But those degrees don’t refer to the bulb’s room temperature or how much heat it gives off. They refer to a piece of carbon burning in a physics lab.
William Thompson and Black Bodies
In 1848, physicist William Thompson proposed a temperature scale in which “absolute zero” was the starting point using increments based on Celsius degrees. The idea caught on and the scale was eventually named for Thompson’s aristocratic title, Lord Kelvin.
Experimentation determined that absolute zero, the temperature at which all normal molecular activity ceases, was 273°C below zero (-459.7°F), or zero degrees Kelvin (K). So by projection, water freezes at 273 degrees and boils at 373 degrees on the Kelvin scale.
What does this have to do with light, you may wonder. When physicists wanted a simpler way to describe color they measured the wavelengths of light radiated by a perfectly light-absorbent material like carbon lampblack known as a “black body” as it was heated to glowing. And they measured that temperature in degrees Kelvin.
The Temperature of Light
As those black bodies were heated, they began to glow, first as red around 3,000K and across the visible spectrum toward blue around 7,500K. You see a similar effect in the flame of a gas stove where the inner, cooler part of the flame burns yellow and the hotter outer tip burns blue. By comparison, the sun glows at an effective color temperature of 5,778K.
How Does Color Temperature Relate to Lig ht Bulbs?
You see descriptive words like soft white, warm white, bright or cool white and daylight on packages of light bulbs. Those are simply marketing terms for the color temperature of the bulb designed to make selection easier for consumers. While color temperature is a precise measure of a bulb’s color output, the descriptive terms are more subjective. But the subjective description is probably all you need when choosing a bulb.
Here’s how those terms relate to actual color temperatures:
Choosing the right color temperature bulb is important to getting the quality of light appropriate to a particular function. But other factors such as light output (watts or lumens), color rendering (CRI), and energy consumption need to be taken into account as well.
Lighting Pros Are In The Know
Lighting is an important part of creating comfortable home and work environments. The pros at Allstar Electrical Services are experts in designing and installing the right lighting for living and work spaces.
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Whatever your electrical needs, call Allstar Electrical at 303.399.7420 or visit our website. Then use our handy on-line forms to request an estimate or set up an appointment. We’ve served the Front Range for over 15 years and are top-rated by the BBB and Angie’s List.