Microwaves

Microwaves are radio waves with a wavelength varying between 1mm (300 MHz) and 1m (300GHz), and the waves travel in the line-of-sight, meaning that they travel in a straight line from the source to the receiver. The waves will be blocked if they encounter an object, and cannot penetrate them if they stand in their path.

Cell phones receive and send microwaves called electromagnetic radiation, along with the kitchen appliance microwave, who use the radiation from the waves to penetrate the foods, heating it up.

https://en.wikipedia.org/wiki/Radio_wave#Speed,_wavelength,_and_frequency

https://en.wikipedia.org/wiki/Microwave

https://en.wikipedia.org/wiki/Line-of-sight_propagation