Before revision: This usage tends not to include effects such as quantum noise in optical communication, which is studied in the sub-branch of coherence theory cc drdo servo servo ethi Principle Physical optics is also the name of an approximation commonly used in optics, electrical engineering and applied physics.
After revision: This usage tends not to include effects such as quantum noise in optical communication, which is studied in the sub-branch of coherence theory (optics)|coherence theorem Principle Physical optics is also the name of an approximation commonly used in optics, electrical engineering and applied physics.