transmitted-intensity-sets-power-and-pressure - Electromagnetic Waves and Radiation Step by Step

Once a polarizer chain fixes the transmitted intensity, that intensity sets both the beam power P = I * A over the illuminated area and the radiation pressure on the surface. The arithmetic is exact only for stated intensity, area, surface orientation, and absorption assumptions. Real beams add finite bandwidth, imperfect polarizers, alignment error, detector calibration, and measurement uncertainty.

Beam power and absorber pressure close from the same transmitted intensity source. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Transmitted intensity sets beam power

A finite beam power is transmitted intensity times illuminated area.

P = I\,A = 9\ \text{W}/\text{m}^{2}\cdot4\ \text{m}^{2}=36\ \text{W}

An absorber pressure is transmitted intensity over speed

The same transmitted intensity and same speed close pressure and power for absorber

p = \frac{I}{c} = 9\ \text{W}/\text{m}^{2}\cdot \frac{1}{6}\Rightarrow \tfrac{3}{2}\ \text{Pa}