Radiation Pressure Perfectly Absorbing Surface — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Radiation Pressure (Perfectly Absorbing Surface) Used to calculate the pressure exerted by electromagnetic radiation on a surface that completely absorbs the incident energy at normal incidence. Total energy delivered in time 't' is U = I A t Total momentum delivered for complete absorption is p = U/c Force exerted is F = p/t = (I A)/c Pressure P = F/A = I/c Applicable only for normal incidence Surface must be 100% absorbing (black body) Wave must be in vacuum or air where refractive index is approx 1 Confusing absorption with reflection; for a perfectly reflecting surface, P = 2I/c Thinking radiation pressure is the same as radiation force; pressure is force per unit area Assuming 'c' changes with medium in basic MCQ scenarios unless specifically stated