What does it mean when waves of laser light are tightly in phase or in step with one another?

• A. Waves are out of phase.
• B. Waves are random in phase.
• C. Waves are tightly in phase or in step with one another.
• D. Waves have no phase relation.

Answer: (C)

When waves are tightly in phase or in step, their peaks line up with peaks and their troughs line up with troughs. This fixed phase relationship means the waves add constructively, so the overall amplitude becomes larger and the beam stays bright and well directed. In a laser, this coherence comes from a fixed phase relationship between emitted photons, producing a highly uniform beam that can create stable interference patterns. If the waves were out of phase or had random phases, they wouldn’t reinforce each other consistently, ending up incoherent with less predictable interference and brightness.