Introduction to Modern Physics: Special Relativity and Quantum Mechanics

Introduction

The fastest speed that humans travel, relative to Earth, is approximately 7,700 m/s. This is the speed that the International Space Station orbits Earth. At this speed something interesting is happening to the astronauts. They are technically aging slower than everyone on Earth. This is one of many bizarre consequences of Albert Einstein's Special Theory of Relativity. While the effect is incredibly small at this speed, as objects travel closer to the speed of light in a vacuum, the effect becomes significantly more pronounced. When Einstein proposed this theory in 1905, physics, and our understanding of the universe, changed forever. As if this wasn't enough of a change, this era also introduced us to the remarkable world of subatomic particles. In this quantum realm, light behaves like a particle and solid matter begins to act like waves. Don't worry if this sounds mind boggling, it is. Now, follow me down rabbit hole and let's see how strange and amazing the universe gets.

Essential Questions

What are the basic tenets of the theory of special relativity?
What is the relationship between mass and energy?
What is the evidence for the particle nature of light?
What is the photoelectric effect?
What is the evidence for the wave nature of matter?

Key Terms

Inertial reference frame - A reference frame in which Newton's 1st Law of Motion is valid.
Theory of special relativity - States that 1) the laws of physics have the same form in all inertial reference frames and 2) Light propagates through empty space with a definite speed independent of the speed of the source or observer.
Rest mass energy - The energy associated with a mass at rest, given by the equation E = mc2.
Photon - A massless particle of light with a discrete energy.
Photoelectric effect - When light shines on a metal surface and electrons are emitted from the surface.
Work function - The minimum amount of energy necessary to eject an electron from an atom.
Quantum number - The orbital level of an electron relative to its ground state.
Ground state - The lowest energy level an electron can occupy.
Uncertainty principle - One cannot measure both the position and momentum of an object precisely at the same time.

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