<P> A photon is a type of elementary particle , the quantum of the electromagnetic field including electromagnetic radiation such as light , and the force carrier for the electromagnetic force ( even when static via virtual particles ) . The photon has zero rest mass and always moves at the speed of light within a vacuum . </P>
<P> A photon is a type of elementary particle , the quantum of the electromagnetic field including electromagnetic radiation such as light , and the force carrier for the electromagnetic force ( even when static via virtual particles ) . The photon has zero rest mass and always moves at the speed of light within a vacuum . </P>
a packet or unit of light energy is called a
a packet or unit of light energy is called a
photon
photon