What is the Inverse Square Law and how is it relevant to mobile telephony?

The intensity of electromagnetic radiation varies with the distance from the source
according to the Inverse Square Law. This means that the radiation's intensity is
inversely proportional to the square of the distance between the source and the
exposed object. Applying this concept to mobile telephony, the further one holds
a mobile phone from the head, the less the (intensity) exposure of the head
and brain to electromagnetic radiation. This accounts for the relative safety of a
hands-free speaker phone mode and, in cars, the use of hands-free car
speaker/microphone kits (where the car's roof acts as the antenna) instead of
the mobile phone itself or an unshielded headset. Regarding car speaker kits for
hands-free mobile telephony, The Australian Government Environmental
Protection Agency states that due to the increased separation between the antenna
(now the car roof) and the user's head, exposure to electromagnetic radiation is
reduced by about 100 times when compared to normal mobile phone use.