🌅 Module 1 · Lesson 2/3
🔥Energy Comes in Packets
How a glowing oven broke physics — and Max Planck fixed it in 1900.
🎯 By the end you will…
- ✓Explain why hot objects glow in different colours
- ✓Understand the “ultraviolet catastrophe”
- ✓Read and use E = hf
Heat a piece of iron and it glows: first dull red, then orange, then yellow-white. Stars do the same — cool stars look red, hot stars look blue. Physicists call this blackbody radiation: the light every object gives off just because it is warm.
Around 1900, the best physics of the day predicted something absurd: any warm object should pour out infinite energy as ultraviolet light. Your cup of tea would be a death ray! Later this was nicknamed the ultraviolet catastrophe.
🎛️Interactive experiment
In December 1900, Max Planck found a formula that matched the experiments perfectly. But it only worked if he assumed something strange: light energy can only be given out in fixed little packets. He called each packet a quantum (Latin for “how much”).
🧮Equation, decoded
Planck's relation — the first quantum equation
What each symbol means
- Energy of one packet (one quantum)
- Planck's constant: 6.626 × 10⁻³⁴ — an unbelievably tiny number
- Frequency: how many times the light wave wiggles per second (its colour)
📖 Say it like a story
Read it like a price list: “Each packet of light costs h times its wiggle-rate.” Blue light wiggles faster than red, so a blue packet is more expensive. A hot object can't afford many expensive ultraviolet packets — and that is exactly what kills the catastrophe.
✅ Check your understanding
Answer all questions to complete the lesson and earn XP.
1. What did classical physics wrongly predict for a warm object?
2. In E = hf, which light has the most energy per packet?
3. Why don't we notice energy “steps” in daily life?
📚 Sources & further reading
- NobelPrize.orgThe Nobel Prize in Physics 1918 — Max PlanckAwarded “in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta”.
- Georgia State UniversityHyperPhysics — Quantum PhysicsA concept map of physics by Prof. Carl Rod Nave. Great for quick, reliable definitions and numbers.
- University of Colorado BoulderPhET Interactive Simulations — Quantum PhenomenaResearch-based simulations (photoelectric effect, lasers, quantum tunnelling…) used in classrooms worldwide.