Microwaves are basically extremely high frequency radio waves, and are made by various types of transmitter. In a mobile phone, they're made by a transmitter chip and an antenna, in a microwave oven they're made by a "magnetron". Their wavelength is usually a couple of centimetres.
Over-exposure to certain types of electromagnetic radiation can be harmful. The higher the frequency of the radiation, the more damage it is likely to cause to the body: microwaves cause internal heating of body tissues. infrared radiation is felt as heat and causes skin burns.
Microwave Ovens and Health. Microwave radiation can heat body tissue the same way it heats food. Exposure to high levels of microwaves can cause a painful burn. ... Additionally, the lens of the eye is particularly sensitive to intense heat, and exposure to high levels of microwaves can cause cataracts.Dec 12, 2017