List three kinds of electromagnetic radiation and either how it is used or how it is prevented

-- Electromagnetic radiation with frequencies between 20 KHz and 80 GHz is generically referred to as "radio waves" and used for "radio" communication.

-- Electromagnetic radiation with frequencies around 2.6GHz (in the US) is used to warm up leftover meatloaf or chicken, or to cook still other foods from scratch.  This radiation is often called "microwave", but technically, "microwave" is actually radio waves with frequencies greater than 3GHz. So the kitchen appliance misses using 'microwaves' by a little bit. (In the US.  "Microwave" cooking appliances in other countries use different frequencies.)

-- Electromagnetic radiation with wavelengths between roughly 400-750 nm is called "visible light".  It is widely used to see stuff with, since human eyes are very effective detectors of this radiation, and we normally have them with us wherever we go.  

-- Electromagnetic radiation with wavelengths less than roughly 400 nm includes ultraviolet rays, X-rays, and gamma rays.  The shorter it is, the more penetrating it is, and the more dangerous it is to human tissue.  

We protect ourselves against exposure to this radiation with a variety of barriers, comprised of thicker and more dense materials as the wavelength decreases and the danger increases.  

Examples include clothing and sunscreen (for ultraviolet rays), thin layers of lead (for X-rays), and thick layers of lead and concrete (for gamma rays).

it becomes positively charged by charging it

one "light year" is the distance that light travels, through vacuum, in one julian year.   that's 365.25 days, of 24 hours each.