where "formula_7" is the resonant wavelength and "m" is the mode number of the ring resonator. This equation means that in order for light to interfere constructively inside the ring resonator, the circumference of the ring must be an integer multiple of the wavelength of the light. As such, the mode number must be a positive integer for resonance to take place. As a result, when the incident light contains multiple wavelengths (such as white light), only the resonant wavelengths will be able to pass through the ring resonator fully.