Modern Physics Lecture Notes

Introduction to Modern Physics

• Modern physics builds on past discoveries.
• Focus on the modern view of the universe: space, time, energy, matter.
• Transition from 19th-century physics to modern physics.

Historical Context

• Foundations laid by Newton, electricity, and magnetism.
• Late 1800s: believed universe mostly understood.
• Puzzles: Atomic spectra, photoelectric effect, heat energy.

Light Phenomena

• Light emission from gases (hydrogen, mercury).
• Atomic spectra and the foundation of quantum physics.

Photoelectric Effect

• Electric currents and the influence of light (ultraviolet).
• Light intensity vs. detection of electric current.

Thermal Energy

• Heat energy and its effects.
• Blue flame and bimetallic strip: mechanical bending and glow.

Technological Revolutions

• Impact of modern physics on technology.
• Imaging, energy harnessing, semiconductors.

Foundations Review

• Newton's mechanics: laws of motion and conservation laws.
• Newton's law of gravitation and electromagnetism.
• Vectors and their algebra in physics.

Newton's Laws of Motion

• First Law: Constant velocity unless acted upon.
• Second Law: F = ma; relates forces and acceleration.
• Third Law: Equal and opposite forces in interactions.

Energy and Momentum

• Kinetic energy and linear momentum.
• Angular momentum and rotational dynamics.
• Conservation principles in isolated systems.

Gravitation

• Gravitational force: mass and distance relation.
• Law of gravitation and its implications.

Electricity and Magnetism

• Maxwell’s Equations: foundation of electromagnetism.
• Electric and magnetic field laws.

Nature of Light

• Light as an electromagnetic wave.
• Wave properties and speed of light in a vacuum.

Relativity

• Transition from Galilean to special relativity.
• Postulates of special relativity.
• Consequences: time dilation, length contraction.

Applications of Relativity

• Thought experiments and real-world implications.
• Concepts of time and simultaneity.

Special Relativity in Practice

• Muons and experimental tests of relativity.
• Time dilation and particle decay.

Doppler Effect

• Classical vs. relativistic Doppler effect.
• Implications for observations in astronomy.

Modern Physics: A Gateway

• Overview of topics and challenges in modern physics.
• Transition from classical to quantum and relativistic physics.