Understanding the Color Change in an Incandescent Lightbulb

Question:

An incandescent lightbulb is controlled by a dimmer. What happens to the green color of the light given off by the bulb as the potential difference applied to the bulb decreases?

Answer:

As the potential difference applied to the incandescent lightbulb decreases, the color of the light emitted shifts towards the red end of the spectrum.

Understanding the Color Change in an Incandescent Lightbulb

Incandescent light bulbs produce light by heating a filament wire to a high temperature until it glows. The color of the light emitted by an incandescent bulb is directly related to the temperature of the filament. When the potential difference applied to the bulb decreases, the filament temperature also decreases.

At higher temperatures, an incandescent bulb emits light that appears white or bluish-white. This light consists of shorter wavelengths, including blue and green. However, as the filament temperature decreases, the emitted light shifts towards longer wavelengths, such as yellow, orange, and finally red.

The green color, which is closer to the blue end of the spectrum, becomes less prominent as the filament temperature decreases. Ultimately, as the potential difference decreases further, the green color diminishes and the light emitted by the bulb shifts towards the red end of the spectrum.

This change in color is a result of the shifting temperatures of the filament and the corresponding wavelengths of light emitted. By adjusting the potential difference applied to the incandescent lightbulb using a dimmer, we can observe these changes in the color of the light produced.