A to B: 5.6 million× apart. End to end, the whole 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 LABThe data track on a CD or DVD is a spiral of pits about a micrometre apart, which is the same size as these wavelengths. Reflections off neighbouring turns interfere, and each frequency survives at its own angle. Tilt a disc under a lamp and you are running a diffraction grating experiment.
→ RUN THIS EXPERIMENT IN THE LIGHT LABEach 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, one minute of exposure. The eventful stretch is the high end, so this bar is zoomed — the strip shows where it sits on the full spectrum:
Illustrative, not a dose calculation: real damage is about total energy absorbed, not just the photon's frequency. The ranking, harmless to harmful as you go right, is real. Please do not eat any irradiated apples!