Which region is defined as the region around the focus where the beam is relatively narrow?

Which region is defined as the region around the focus where the beam is relatively narrow?

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

Answer: (C)

The key idea is understanding where a focused beam stays narrow around its point of tightest focus. This region is called the focal zone. It surrounds the focus and is where the beam width remains relatively small, so the beam maintains good lateral resolution and concentrates energy there. Before reaching the focus, the beam is still converging and gradually narrows, which is known as the near field. After the focus, the beam begins to diverge and widens, which corresponds to the far field. The term transition zone isn’t the standard label for this particular region around the focus.

The key idea is understanding where a focused beam stays narrow around its point of tightest focus. This region is called the focal zone. It surrounds the focus and is where the beam width remains relatively small, so the beam maintains good lateral resolution and concentrates energy there. Before reaching the focus, the beam is still converging and gradually narrows, which is known as the near field. After the focus, the beam begins to diverge and widens, which corresponds to the far field. The term transition zone isn’t the standard label for this particular region around the focus.