A curved spike line tends to produce a beam with a focus that is shallower or deeper?

A curved spike line tends to produce a beam with a focus that is shallower or deeper?

• A. Shallower
• B. Deeper
• C. The Same
• D. Variable

Answer: (A)

Curving the spike line changes how the wavefront is phased across the aperture. That curvature introduces phase errors and higher‑order aberrations, so the beam cannot constructively focus as well along the propagation direction. The energy that would stay confined over a longer axial range is spread out more quickly, shrinking the axial region that stays in good focus. In other words, the depth of focus becomes shallower when the spike line is curved. If the line were straight, those phase errors would be minimized and the focus could remain tighter along the axis.

Curving the spike line changes how the wavefront is phased across the aperture. That curvature introduces phase errors and higher‑order aberrations, so the beam cannot constructively focus as well along the propagation direction. The energy that would stay confined over a longer axial range is spread out more quickly, shrinking the axial region that stays in good focus. In other words, the depth of focus becomes shallower when the spike line is curved. If the line were straight, those phase errors would be minimized and the focus could remain tighter along the axis.