Which zone describes the near-field region where the beam is still developing before the focal region?

Which zone describes the near-field region where the beam is still developing before the focal region?

• A. Fraunhofer zone
• B. Focal zone
• C. Fresnel zone
• D. Near-field region

Answer: (C)

In wave propagation, the space close to an aperture or lens is the Fresnel zone—the near-field region where the wavefront hasn’t yet形成 its final shape and the intensity pattern evolves as it travels toward the focus. This is the region where diffraction effects are significant and the beam is still developing before reaching the focal point. Beyond this near-field lies the Fraunhofer zone, the far-field where the pattern becomes essentially the Fourier transform of the aperture. The term “near-field region” is generic, and the focus area is not a standard designation; the specific near-field zone where the beam is still building toward the focus is the Fresnel zone.

In wave propagation, the space close to an aperture or lens is the Fresnel zone—the near-field region where the wavefront hasn’t yet形成 its final shape and the intensity pattern evolves as it travels toward the focus. This is the region where diffraction effects are significant and the beam is still developing before reaching the focal point. Beyond this near-field lies the Fraunhofer zone, the far-field where the pattern becomes essentially the Fourier transform of the aperture. The term “near-field region” is generic, and the focus area is not a standard designation; the specific near-field zone where the beam is still building toward the focus is the Fresnel zone.