Addiction: Central nervous system (CNS) stimulants are addictive, even if they are not abused. Many factors, including the patient's personal history, the type of stimulant that is being taken, the dose of the drug, and duration of use, influence how likely an individual is to become addicted.
The source of all waves - mechanical or electromagnetic - is something that is vibrating. Matthew Donovan.
The Sun is a natural source for visible light waves and our eyes see the reflection of this sunlight off the objects around us. The color of an object that we see is the color of light reflected. All other colors are absorbed. Light bulbs are another source of visible light waves.