A scientific diagram illustrating the concept of energy spectrum. The diagram consists of two overlapping graphs, one in red and the other in green, showing the distribution of energy levels. The red graph represents the energy spectrum of a sample of particles, while the green graph represents the energy spectrum of a sample of particles with a different energy distribution. The graphs are overlaid on a white background with a green header that reads 'ENERGY SPECTRUM'. The diagram also includes a small image of a triangle in the top left corner, which appears to be a logo or symbol.