Figure 6-25: The Transparency of Earth’s Atmosphere This graph shows the percentage of radiation that can penetrate Earth’s atmosphere at different wavelengths. Regions in which the curve is high are called “windows,” because the atmosphere is relatively transparent at those wavelengths. There are also three wavelength ranges in which the atmosphere is opaque and the curve is near zero. At wavelengths where the atmosphere is opaque, ground-based telescopes cannot receive light from space because it is either absorbed or reflected by the atmosphere.