inverse squared means that it decreases with respect to the square of the distance. this is known as a polynomial and could colloquially be referred to as exponential because it decreases really fast. but it's not exactly accurate.

this means like, 1/(r^2)

so, at 1 meter, intensity = 100%

at 2 meters, intensity = 25%

at 3 meters, intensity = 1/9

at 4 meters, intensity = 1/16

exponential means that it decreases according to some variable to the power of the distance

this means like 0.1^r

so at 1 meter, intensity = 100%

at two meters, intensity = 10%

at three meters, intensity = 1%

anyway, light intensity decreases according to inverse squared law and i have personally done physics experiments that confirm this.

this isn't "exponential" but it is rapid decay.