Rays
There are multiple types of waves which vary due to change in frequency and/or wavelength. This means that things look the way they do because their waves are unique. Blue looks like blue because of this. Or that we can hear radios and see light. But not all rays are helpful. The higher in frequency or lower in wavelength you go the more harmful the waves are. The most harmful being gamma rays. Phones give out radio frequency. This is quite a low frequency but when you are in contact with the receiver or emitter your skin tends to absorb this energy.
About different rays
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