OpenCV 4 for Secret Agents - Second Edition

Understanding the spectrum

The universe is flooded with light, or electromagnetic radiation, and astronomers can use all wavelengths to capture images of distant objects. However, the Earth's atmosphere partly or wholly reflects some wavelengths of light or radiation back into outer space, so typically we deal with more limited ranges of wavelengths in imaging on Earth. NASA provides the following illustration, showing various wavelengths of electromagnetic radiation, their day-to-day importance to human beings, and their ability (or inability) to penetrate the Earth's atmosphere:

Note that the axis in the preceding diagram runs from longer ...