Let's say you have a monochromatic laser beam directed towards a light sensor. As you move the sensor away from the laser, the intensity read by the sensor will decrease because of scattering on air molecules (extinction). Since intensity is proportional to the square of the E-field amplitude of the EM wave, this means that the E-field amplitude has decreased in the beam. My question is : how? In my mind, the only way to decrease the E-field is if the air molecules produce an E-field that interferes destructively with the incident E-field. However, by treating air molecules as electrons oscillating on a spring, you get constructive interference for visible incident light.