Photon-photon Collisions

When photons collide, they create electrons due to the energy created during the collision. But if that is true, shouldn't the photon collision create an electron-positron pair?
- Anonymous (age 10)
Rhode Island

If a photon collides with an atom, the photon can impart enough energy to the atom to eject an electron.  The atom will then have a plus charge of  +1 e the ejected electron has charge -1;  the net charge before and after the collision is zero.     If an energetic photon collides with something and an electron is not ejected from the object, then if there is enough energy an electron-positron pair may be ejected.  When a photon collides with another photon an electron positron pair may be produced.  Again the net charge before and after is the same, zero.

In all cases charge and energy are conserved.

LeeH

 

(published on 03/07/2018)