FM radio and green laser light are the same phenomenon, 5.6 million× apart in frequency. End to end, this bar covers a ten-quadrillion-fold range. Drag a marker.
Visible light, magnified:
Glass slows every frequency on this strip by a slightly different amount, so each one bends through a slightly different angle, and white light fans out into exactly the band drawn above. Newton did it with a prism in 1666 and named seven colours, but seven was taste: the band is a continuum, one colour per frequency, no seams.
→ RUN THIS EXPERIMENT IN THE LIGHT LABDo you even know what a CD looks like up close, in real life? The Light Lab has one: tilt it under a lamp, then dive a hundred-thousand-fold into its surface to the micrometre-sized pits that build the rainbow.
→ EXPLORE THE PHYSICSEach droplet refracts sunlight on the way in, reflects it off the back, and refracts it again on the way out. Red exits at about 42 degrees from the antisolar point and violet nearer 40, which is why the bow is a band and red is on the outside. Sun behind you, mist in front, look at your shadow's head height.
→ RUN THIS EXPERIMENT IN THE LIGHT LABAir molecules scatter light in proportion to the fourth power of its frequency, so the blue end of this strip scatters roughly ten times as strongly as the red end. Look anywhere but at the sun and scattered blue is what reaches you. At sunset the light crosses so much air that the blue has been scattered away en route, and what survives the trip is the red. Try it: drag the sun down.
For scale: point a beam at an apple. Dial one is frequency. The eventful stretch is the high end, so this bar is zoomed; the strip shows where the window sits on the full spectrum:
Dial two is power, held on the apple for 60 s:
The two dials are the whole lesson. Frequency decides what each photon can do: nudge, excite, break a bond, or ionize. Power times time decides how much arrives. Pour megawatts into radio and it cooks. A gamma trickle cannot warm a thing, yet every photon still ionizes. That is why your router is harmless and a sterilizer plant is not. Please do not eat any irradiated apples!
Everything on this site runs the real physics in miniature: Planck's E = hf behind every readout, Snell and dispersion in the prism, the grating equation on a real 1.6 µm track pitch in the CD, the 42° droplet cone, Rayleigh's 1/λ⁴ in the sky. Illustrative in scale, honest in mechanism — if a number here disagrees with your textbook, trust the textbook and tell us. Studio lighting HDRI by Poly Haven (CC0).
Built by Amy Robinson Sterling @amyneurons, with Fable and Sol.