The average intensity across the beam's entire cross-sectional area is called what?

The average intensity across the beam's entire cross-sectional area is called what?

• A. Spatial peak intensity or Isp
• B. Pulse average intensity or Ipa
• C. Spatial average intensity or Isa
• D. Temporal

Answer: (C)

Intensity describes how much power passes through each area of the beam. Across a beam, the brightness isn’t the same everywhere, so we distinguish between the value at a single point (the peak) and the average over the whole cross section. The spatial average intensity is the mean intensity across the entire cross-section, essentially the total power divided by the cross-sectional area. In equation form, Isa = P / A, or Isa = (1/A) ∫∫ I(x,y) dA. This is different from the spatial peak intensity, which is the maximum value anywhere in the cross-section, and from temporal averages, which average over time rather than space. So the average across the beam’s cross-section is spatial average intensity.

Intensity describes how much power passes through each area of the beam. Across a beam, the brightness isn’t the same everywhere, so we distinguish between the value at a single point (the peak) and the average over the whole cross section. The spatial average intensity is the mean intensity across the entire cross-section, essentially the total power divided by the cross-sectional area. In equation form, Isa = P / A, or Isa = (1/A) ∫∫ I(x,y) dA. This is different from the spatial peak intensity, which is the maximum value anywhere in the cross-section, and from temporal averages, which average over time rather than space. So the average across the beam’s cross-section is spatial average intensity.