What is the difference between classical physics and modern physics?

Explanation

Classical physics is mainly physics before the 19th century which mainly consists of Newtonian physics, some principles by Galelio and it mainly focuses on macroscopic observation of matter.
Whereas modern physics mainly comprises physics after the 19th century which includes disciples like electromagnetism, wave nature of light, dual nature, etc.
It includes quantum mechanics which arose due to the works of Sir Max Planck in the fields of quantum theory of light and theory about black body radiations.
In quantum physics, one mainly focuses on the study of quantization of energy in the atomic level, it also includes theories like Bohr's theory of atomic model in which he discussed quantization of energy of electrons(fixed discrete levels of orbits).
In a nutshell we can assume that modern physics deals with fundamental theories of nature at small scales , low energy levels of atoms and subatomic particles.
Like , in quantum mechanics ,we study about particles having discrete values of momentum, energy and other quantities and have dual nature (i.e characteristics of both particle as well as wave) and there is uncertainty about position and momentum at the same time of a particle (also called Heisenberg's ​uncertainty principle).