1. The problem statement, all variables and given/known data Both Q1 = Q2 = +5E-6 and are harnessed to screen and in a vacuum. ----Q1---A----Q2------B--------P this is x axis, A and B are distances 2. Relevant equations kQ/r^2 3. The attempt at a solution So the E field at point P is KQ1/(A+B)^2 + KQ2/(B)^2 My question is Why isnt Q1 E field affected by the repulsion of the two charges. IE if photons carry the force of the charged particle, why arent the photons affected by the presence of Q2 emitting photons 360 degrees. So to the left of Q2, Q2 sends its signed wave to the left while a same signed wave is moving to the right from Q1. Shouldnt they interact, that is how they would repel if not anchored to the screen.