Beam divergence is defined as what?

Beam divergence is defined as what?

• A. The decrease in beam diameter with distance
• B. Change in coherence length
• C. Change in wavelength
• D. The increase in beam diameter (spread) as the distance increases from the laser.

Answer: (D)

Beam divergence describes how a laser beam spreads as it travels away from the source. Because light behaves as a wave with a finite aperture, the beam cannot stay perfectly confined and its cross‑section must grow with distance. The divergence is the angular measure of that spreading, so the beam diameter increases as distance from the laser increases. Conceptually, you can think of it as the beam fanning out as it propagates, with the diameter growing roughly in proportion to distance for a given divergence angle. In practical terms, a larger divergence angle means the beam expands more quickly, reducing intensity with distance. This matches the idea that the beam’s spread (increase in diameter) with distance is what divergence is about. The other choices describe changes in properties that aren’t about geometric spreading: decreasing diameter with distance isn’t how a typical beam propagates, coherence length concerns phase relationships, and wavelength is a spectral property that doesn’t change simply due to distance in a uniform medium.

Beam divergence describes how a laser beam spreads as it travels away from the source. Because light behaves as a wave with a finite aperture, the beam cannot stay perfectly confined and its cross‑section must grow with distance. The divergence is the angular measure of that spreading, so the beam diameter increases as distance from the laser increases. Conceptually, you can think of it as the beam fanning out as it propagates, with the diameter growing roughly in proportion to distance for a given divergence angle. In practical terms, a larger divergence angle means the beam expands more quickly, reducing intensity with distance. This matches the idea that the beam’s spread (increase in diameter) with distance is what divergence is about. The other choices describe changes in properties that aren’t about geometric spreading: decreasing diameter with distance isn’t how a typical beam propagates, coherence length concerns phase relationships, and wavelength is a spectral property that doesn’t change simply due to distance in a uniform medium.