This lecture discusses the conservation of momentum and its association with electromagnetic fields, emphasizing the lack of conservation in certain scenarios. It also covers the relativistic aspects of energy and momentum, including the energy-momentum relation for photons. The lecture further explores the temporal averages and definitions of intensity, along with examples of plane wave emissions and the impact of electric fields on the human body. The presentation concludes with practical examples related to solar emissions and the effects of electric fields on the human body.