When multiple colored filters of the same color cover a light source, the light's wavelength and frequency remain unchanged. The filters selectively absorb certain wavelengths of light while allowing others to pass through.
Each colored filter has its specific absorption characteristics, which means it absorbs certain wavelengths of light and transmits or allows others to pass. When multiple filters of the same color are stacked, the combined effect is essentially equivalent to using a single filter of that color, with the intensity of the transmitted light reduced with each additional filter.
For example, if you stack multiple red filters on a light source, each filter absorbs a portion of the incident light, allowing only the red wavelengths to pass through. The transmitted light will still consist of red wavelengths, and its frequency and wavelength will remain the same.
The primary effect of adding multiple filters is a reduction in the intensity or brightness of the transmitted light. Each filter absorbs some of the incident light, leading to a cumulative decrease in the overall light intensity. However, the fundamental properties of the light, such as its wavelength and frequency, are not altered by the filters.