👉 Blue light is the visible portion of sunlight that reaches Earth's atmosphere, predominantly in the blue part of the spectrum. It causes discomfort for human eyes. Definition: Blue light refers to the blue or violet spectral component of the electromagnetic spectrum, which includes wavelengths from 400-700 nanometers (nm). It appears blue due to its dispersion and absorption properties, allowing certain colors to pass through more easily than others. For example, red light is typically observed in the visible range and produces a warm yellow color, while blue light can cause eye strain and headaches if exposure exceeds specific threshold wavelengths.