beam-power-pressure-three-row-scan - Electromagnetic Waves and Polarization Step by Step

Transmitted intensity drives both finite beam power and absorber pressure in parallel ledgers. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Six watts per square metre gives one pascal

At fixed area 4 square metres and speed 6 metres per second, transmitted intensity 6 watts per square metre gives pressure 1 pascal.

P=IA=6\ \text{W}/\text{m}^{2}\cdot4\ \text{m}^{2}=24\ \text{W},\quad p=I/c=1\ \text{Pa}

Nine watts per square metre gives three-halves pascals

The same area and speed with intensity 9 watts per square metre gives power 36 watts and pressure 3/2 pascals.

P=9\ \text{W}/\text{m}^{2}\cdot4\ \text{m}^{2}=36\ \text{W},\quad p=\tfrac{3}{2}\ \text{Pa}

Twelve watts per square metre gives two pascals

The third intensity is 12 watts per square metre. Power rises to 48 watts while pressure rises to 2 pascals.

P=12\ \text{W}/\text{m}^{2}\cdot4\ \text{m}^{2}=48\ \text{W},\quad p=2\ \text{Pa}