I'm so lost... can someone please explain :( thanx Red light with wavelength 700 nm is passed through a two-slit apparatus. At teh same time, monochromatic visible light with another wvelength passes through teh same apparatus. As a result, most of the pattern that appears on the screen is a mixture of two colors; however, the center of the third bright fringe (m=3) of the red light appears pure red, with none of other color. What are the possible wavelengths of the second type of visible light? Do you need to know the slit spacing to answer this question? Why or why not?