Physics 5 — Modern Physics
Photons, the photoelectric effect, matter waves, special relativity’s γ, E = mc², and half-life dating.
Around 1900, physics hit two walls: light insisted on arriving in chunks, and fast-moving clocks insisted on running slow. The repairs — quantum mechanics and relativity — sound like science fiction, yet they run your phone's chips and your car's GPS every second.
- 01 Light comes in chunks: E = h·f ELI5: light isn't a smooth stream — it arrives in tiny packets called photons, each carrying energy E = h·f (frequency times Planck's constant). That…
- 02 The photoelectric effect — Einstein's Nobel ELI5: shine light on metal and it kicks out electrons — but only if each individual photon carries enough energy to pay the "exit fee" (the work…
- 03 Matter waves ELI5: de Broglie's beautiful heresy — if waves can act like particles, then particles act like waves, with wavelength λ = h/(m·v). For everyday objects λ…
- 04 Special relativity — γ ELI5: nothing outruns light, and the universe enforces it with the Lorentz factor γ = 1/√(1 − v²/c²). At human speeds γ ≈ 1 and you notice nothing; approach…
- 05 E = mc² and half-life ELI5: mass is frozen energy at a staggering exchange rate, c². Convert a single gram completely and you get a power-plant's worth of energy.