Which term describes energy composed of one wavelength?

• A. Coherent energy
• B. Collimated energy
• C. Monochromatic energy
• D. Fluence

Answer: (C)

Monochromatic energy describes energy composed of a single wavelength. The prefix “mono-” means one, and “chromatic” relates to color or wavelength, so monochromatic light has essentially one spectral line. This is what laser light is often described as, since it has a very narrow range of wavelengths.

Other terms describe different properties: coherent energy refers to a fixed phase relationship between waves, which is about timing and wavefronts rather than spectral content; collimated energy means the beam travels in parallel directions with little divergence; fluence is the amount of energy per unit area, not about the wavelengths present.