What is the Dominant Wavelength of an LED?
The Dominant Wavelength of an LED is the wavelength of the photons that an LED emits the vast majority of the time.
In other words, the photons that the LED emits will that of the value of the dominant wavelength specified in the LED's datasheet.
All LEDs emit photons in order to emit light. The wavelength of the photons that an LED emits determines the LED's color. For example, red LEDs have wavelengths of around 633 to 660 nanometers, depending on whether it's super red, high efficiency red, or ultra red. The wavelength determines the color and brightness of an LED.
On a datasheet for an LED, you can get a feel for the characteristics of an LED by viewing 2 characteristics of the LED, its dominant wavelength, which is the the wavelength the LED emits the majority of the time, and its peak emission wavelength, which is the maximum wavelength that the LED will achieve at times. These two characteristics shouldn't vary much.
The dominant wavelength is a specification that shows the wavelength that the LED will emit the majority of the time. The LED may emit a slightly higher wavelength at times, called the peak emission wavelength. This may vary the color that the LED emits slightly but for the most part cannot be noticed.
These 2 specifications serve to show the variance in wavelengths that an LED can produce.