A beam of photons with the same frequency and phase is termed what?

• A. Monochromatic Light
• B. Coherent Light
• C. Plume
• D. Spot Size

Answer: (B)

Coherence describes how well the phase of a light wave is correlated across the beam. When photons share the same frequency and maintain a constant phase relationship, the light is coherent, which allows stable interference and predictable wave behavior. Monochromatic light refers to a single color or frequency, but that alone doesn’t guarantee a fixed phase relationship among all photons; you can have many photons of the same frequency with random phases, which would be incoherent. Plume and spot size aren’t about the phase or frequency properties of light—plume isn’t a standard light property, and spot size describes the beam’s cross-sectional area.