Absorbing Surface Pressure Is Irradiance over Speed - Electromagnetic Waves and Radiation Step by Step

A perfectly absorbing surface feels radiation pressure P = E / c, the irradiance divided by the speed of light, because each photon hands its momentum over. The factor of c in the denominator is what makes sunlight push so weakly. The exact value holds only for the stated irradiance and a perfectly black, normal surface; real surfaces reflect partly and the beam and calibration carry uncertainty.

An absorber pressure claim divides checked irradiance by stated training speed. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Absorber pressure is irradiance over speed

The speed is an explicit training value, not the real speed of light.

p=\frac{I}{c}=\frac{6}{6}=1\ \text{Pa}

The absorber mode sets the multiplier

For an absorber the multiplier is one.

\hbox{mode}=\hbox{absorber},\quad p=1\ \text{Pa}