I don't know for certain but I expect wind power is the least widely used (wave power and tidal power are not used commercially at all yet, I believe). A lot depends on your definition of 'widely used'. Do you mean megawatts generated in a given time?
Yes
It is widely used but not as much as hydrocarbons and hydroelectric. Japan has extensive nuclear facilities, Europe has many.
Pelamis Wave Energy Converter
y
Yes
eletrical
Yes.
Visible Light is used with Spectroscopes.
Wave energy is being used all around the world. The Bay of Fundy in Canada, and the River Rance in France are the biggest.
It moves energy through space.
You can use them with fishing or when your sailing. it will push your boat/fish round. Also, waves can be used to generate energy. This is a sustainable way to get energy, and is simply known as Wave Energy, or Wave Power.