A region around the focus where the beam is relatively narrow.

A region around the focus where the beam is relatively narrow.

• A. Near field
• B. Focal zone
• C. Far field
• D. Transition zone

Answer: (B)

Understanding how a focused beam behaves along its path helps explain this. The region around the focus where the beam remains relatively narrow is the focal zone. This is the depth range where the focusing element keeps energy concentrated so the beam width stays small, giving better lateral resolution. As you approach the focal point, the beam narrows; at and near the focus it is at its minimum width, and beyond it the beam begins to diverge, becoming wider in the far field. The near field lies before the focus, where the beam is still converging toward the focal point, and the far field lies after the focus, where the beam has spread out. The term transition zone isn’t the standard designation for this specific region.

Understanding how a focused beam behaves along its path helps explain this. The region around the focus where the beam remains relatively narrow is the focal zone. This is the depth range where the focusing element keeps energy concentrated so the beam width stays small, giving better lateral resolution. As you approach the focal point, the beam narrows; at and near the focus it is at its minimum width, and beyond it the beam begins to diverge, becoming wider in the far field. The near field lies before the focus, where the beam is still converging toward the focal point, and the far field lies after the focus, where the beam has spread out. The term transition zone isn’t the standard designation for this specific region.