Wave Optics: Interference & Diffraction
📋 What it is
Light behaves like a wave — it can bend around edges (diffraction) and add up or cancel (interference).
🗣️ Coach says
Light isn’t only straight rays; it’s also a wave. Waves spread when they pass a narrow gap or edge (diffraction) and, when two light waves overlap, they can reinforce (bright) or cancel (dark) — interference. These patterns are the proof that light is a wave.
🧠 Memory hook
Light is a wave: it bends round edges (diffraction) and adds/cancels (interference).
😂 Giggle
Why did the laser beam feel special?
Because it was always on point and never scattered!
😲 Whoa!
The rainbow shimmer on a soap bubble or CD isn’t dye — it’s light waves interfering, adding some colours and cancelling others.
✅ Quick check: What makes the colourful shimmer on a soap bubble?
Say your answer out loud first — then reveal.
Interference — light waves reflecting off the bubble’s two surfaces overlap, reinforcing some colours and cancelling others.
Thin-film interference, not pigment, creates the colours.
🧪 Try it! (2 minutes)
Tilt a CD under a light and watch the rainbow shift — that’s diffraction and interference at work.