The Australian research focused on the thermal effects or specific absorption rate (SAR) of radio frequency radiation - a measure of its actual effects on brain tissue, whereas the earlier study simply looked at electromagnetic radiation levels.

BBC: Hands-free mobiles given safety boost

The result is far less low-frequency radiation.

ECONOMIST: Monitor

Interestingly, the movement includes many who still believe that the lower frequency radiation from power lines and electric appliances and motors also poses a cancer threat, in spite of the fact that 30 years of research has shown no effects.

FORBES: Do Cell Phones Cause Brain Cancer? The Diehards Cling Desperately To Opinion

The concerns stem from the emissions of radio frequency (RF) radiation by both the handsets and the base stations that transmit and receive the signals.

BBC: Public Petitions Committee

The other, which faces a specialised type of solar cell made of a material called indium gallium arsenide, is sculpted into a structure called a photonic crystal that causes it to emit infra-red radiation selectively at the frequency best absorbed by the cell.

ECONOMIST: Solar power