This fourth volume of the general course of physics is devoted to physical optics and is a natural continuation of the previous volume, which sets forth the doctrine of electric magnetic phenomena. Physical optics is considered in it mainly from the wave (of course, electromagnetic) point of view. Probes of quantum optics are only partially affected. The idea of photons and the radiation process as a quantum transition of atomic systems from one energy state to another is given. This is necessary to introduce the concept of induced radiation and explain the principles of lasers. However, a systematic presentation of the basics of quantum optics, to the extent that it is possible to do so within the framework of general physics, as well as related quantum phenomena (photo effect, Compton effect, spectral patterns, luminescence, Zeeman effect, Stark effect, etc.) ), is intended to be given in the fifth volume, where atomic physics in the broad sense of the word will be expounded. This is a continuation of the publication of the 1st volume of Mechanics2 volume of Thermodynamics and Molecular Physics3 volume of Electricity