H
Hardness
In general means the mechanical resistance that a material opposes the mechanical penetration of a softer, equally tough or tougher body. The is measured by the comparison of several materials or material conditions
HF radiation
High frequency electromagnetic waves are emitted for the wireless transfer of data in frequencies between 100 kHz and 300 GHz. This sees electrical and magnetic fields merge to form an electromagnetic wave. High frequency radiation is used primarily by radio and television broadcasters, by radar, mobile phones and cordless phones, microwaves and baby monitors. The reason for this is the fact that their waves spread quickly and also the long range of .