The phrase "wavelength range" refers to a group or spectrum of different wavelengths for a particular type of wave. It indicates the span or variety of wavelengths that are included within a specific range. Full definition
Several filters were used to sample narrow wavelength ranges. (hubblesite.org)
But most are very tiny and only work at very small wavelength ranges, rendering them less impressive to the average observer. (sciencedaily.com)
Results of a field experiment on studying solar radiation passing in the visible wavelength range are described with the model aerosol media created in the surface atmosphere. (link.springer.com)