Short Answer
Classical physics explains the behaviour of objects that we see in daily life, such as moving cars, falling stones, heat, sound, and light at normal speeds. It follows simple and predictable laws made by Newton, Maxwell, and other scientists. These laws work well for large objects and slow speeds.
Modern physics deals with very small particles, very high speeds, and very high energies. It explains things that classical physics cannot, such as atomic structure, behaviour of electrons, nuclear energy, relativity, and quantum effects. Modern physics helps us understand advanced technologies like lasers, GPS, semiconductors, and nuclear reactors.
Detailed Explanation :
Difference between classical and modern physics
The difference between classical and modern physics lies in the type of physical situations they explain, the scale at which they work, and the principles they follow. Classical physics deals with everyday situations that we experience around us. It explains motion, force, heat, sound, electricity, magnetism, and light at normal speeds using simple and predictable laws. Classical physics assumes that the world works in a continuous and deterministic way, meaning that everything follows fixed rules and outcomes can be predicted accurately.
Modern physics, on the other hand, deals with conditions that classical physics fails to explain. These include extremely small scales like atoms and subatomic particles, extremely high speeds near the speed of light, and extremely strong gravitational fields. In such conditions, the laws of classical physics do not give correct results. Therefore, modern physics introduces new theories like relativity and quantum mechanics to explain the behaviour of matter and energy.
Classical physics is based mainly on Newtonian mechanics, Maxwell’s theory of electromagnetism, thermodynamics, and wave theory. Newton’s laws explain motion and forces, while Maxwell’s equations describe electricity and magnetism. Classical thermodynamics explains heat and energy transfer. These ideas work very well for macroscopic objects like planets, cars, buildings, machines, and even everyday activities like walking or running.
Modern physics came into existence in the early 20th century when scientists discovered that classical laws could not explain some phenomena. Experiments on blackbody radiation, photoelectric effect, atomic spectra, and high-speed particles showed that new principles were required. This led to the development of quantum mechanics, which explains the behaviour of very small particles, and Einstein’s relativity, which explains objects moving at high speeds and the effect of gravity on space and time.
Classical physics (Subheading)
Classical physics works when objects are large in size and move at speeds much lower than the speed of light. It assumes that time and space are fixed, meaning they do not change for different observers. Classical physics also assumes that energy and matter behave in a continuous manner.
In classical mechanics, objects have definite positions and velocities at all times. Motion can be predicted if forces are known. For example, if you throw a ball, classical physics can calculate its path, speed, and distance. It works well for planets, vehicles, machines, and everyday forces.
Classical electromagnetism explains how electric charges, electric fields, magnetic fields, and electromagnetic waves behave. Light is treated mostly as a wave in classical physics. Heat is explained through classical thermodynamics, which describes how energy flows from hot objects to cold objects.
However, classical physics fails in certain situations. It cannot explain how electrons stay in stable orbits around the nucleus, why light sometimes behaves like a particle, or why time changes depending on speed. It also cannot describe nuclear reactions, atomic spectra, or the behaviour of materials at very small scales.
Modern physics (Subheading)
Modern physics deals with the limitations of classical physics and introduces new concepts to understand the physical world more deeply. It works at atomic, subatomic, and cosmic scales. It shows that matter and energy behave differently than classical laws predict.
One major part of modern physics is quantum mechanics. It explains the behaviour of tiny particles like electrons and photons. Quantum theory shows that energy is not continuous but comes in small packets called quanta. It also explains wave particle duality, where light and particles behave both as waves and particles. Quantum mechanics describes atomic structure, chemical bonding, semiconductors, and modern electronic devices.
Another major part is relativity, given by Albert Einstein. Special relativity explains how time, space, and mass change when objects move near the speed of light. It introduces concepts like time dilation and mass energy equivalence, expressed by the famous equation E = mc². General relativity explains gravity as the bending of space and time by massive objects. Modern physics also studies nuclear forces, particle physics, cosmology, and the origin of the universe.
Modern physics is essential for many technologies like lasers, X ray machines, MRI scanners, nuclear power, satellites, GPS systems, and digital electronics. None of these can be understood using only classical physics.
Conclusion
Classical physics explains everyday events using simple and predictable laws, while modern physics explains advanced and extreme situations involving very small particles, very high speeds, and strong gravitational effects. Classical physics is suitable for slow moving and large objects, while modern physics is required for understanding atomic structure, relativity, and advanced technologies. Both branches together help us understand the physical world completely.