The eye can detect 5 x 104 photons per square meter per sec of green light (λ=5000Å) while the ear can detect 10-13(W/m2). The factor by which the eye is more sensitive as a power detector than the ear is close to

E=123755000=2.475eV≈4×10−19JSo the minimum intensity to which the eye can respondIEye =( Photon flux )×( Energy of a photon )⇒IEye =5×104×4×10−19≃2×10−14W/m2Now as lesser the intensity required by a detector for detection, more sensitive it will beSEye SEar =IEar IEye =10−132×10−14=5 i.e., as intensity (power) detector, the eye is five times more sensitive than ear.