light and quantum physics

Here are some refrences that explain the packet behaviour as well as electromagnetic behaviour of light http://www.victorianweb.org/science/fresnel.html http://www.physics.uc.edu/suranyi/Modern_physics/Lecture_Notes/modern_physics2.html http://physics.syr.edu/courses/modules/LIGHTCONE/maxwell.html http://en.wikipedia.org/wiki/Light

It has two definations. Light can be treated as firstly a wave which travel in straight lines . The second defination is that light can be treated as an electrmagnetic wave in which the light travels in the perpendicular direction of the signal movement. The second defination was proved later by young's open slit experiment which caused maximan and minima at certain points.