Quantum physics and modern physics are related but not identical terms. Here's an explanation of the difference between the two:
Modern physics: Modern physics refers to the physics developed in the early 20th century and beyond, which encompasses various branches of physics that emerged after classical physics. It includes both classical physics and quantum physics. Modern physics incorporates the revolutionary theories and discoveries that challenged and expanded our understanding of the physical world. It encompasses areas such as relativity theory (both special and general relativity) and quantum mechanics.
Quantum physics: Quantum physics, also known as quantum mechanics, is a specific branch of modern physics that deals with the behavior of matter and energy on the atomic and subatomic scale. It provides a framework for understanding the fundamental particles and their interactions, the wave-particle duality, the probabilistic nature of measurements, and the quantization of energy levels. Quantum physics describes phenomena that cannot be explained by classical physics, which is based on deterministic laws and continuous quantities.
In summary, modern physics is a broader term that encompasses various branches of physics, including classical physics, relativity theory, and quantum physics. Quantum physics, on the other hand, specifically refers to the branch of modern physics that focuses on the principles and phenomena at the microscopic scale, where quantum effects dominate and classical physics breaks down.