light is ac current, vibrating electric force.

every atom is an ac generator. electrons vibrate on the plane perpendicular to the radius due to their momentum. 

assume your room is a vacuum chamber, if the distance between the screen and your eyes is r, the repulsion force between the electrons on the screen and your eyes is f=Ke x ee/rr. that force is the carrier of light.

if the electrons on the screen vibrate at a frequency, electrons on your eyes will get f strength of ac current at the same frequency.

there is no time delay in the vacuum space, a force has zero mass, from f=ma, any forces have infinite acceleration, all forces are instantaneous in the vacuum space.

forces pass through matters/mediums have limited speed, due to f=ma, all matters have mass.