Question 1: Cell phones use sound waves to send text messages.

It's electromagnetic waves! The old mobile phone used 900MHZ electromagnetic wave, and then it had 1800MHZ, and now it is 3000MHZ (that is, 3G).

Electromagnetic wave (also known as electromagnetic radiation) is an electric field and a magnetic field that oscillate in the same phase and are perpendicular to each other. It moves in the form of waves in space, and its propagation direction is perpendicular to the plane formed by electric field and magnetic field, effectively transmitting energy and momentum.

Electromagnetic waves can be classified by frequency, from low frequency to high frequency, including radio waves, microwaves, infrared rays, visible light, ultraviolet rays, X rays and gamma rays.

So radio waves are part of electromagnetic waves.