← all cardsTopic 11 · Wave Motion · EM spectrum
Visible-band numbers
● VERBATIM — examined word-for-wordVisible: 400 nm (violet) – 700 nm (red). f = c/λ: 4.3 × 10¹⁴ Hz (red, 700 nm) to 7.5 × 10¹⁴ Hz (violet, 400 nm). Trap: minimum frequency pairs with the LONGEST wavelength.
f = c/λWhat this actually means
Memorise the window: 400 nm violet to 700 nm red. The rest of the spectrum is anchored around it: radio, micro, IR below; UV, X, gamma above.
Frequencies come from f = c/λ: red at 700 nm gives 4.3 × 10¹⁴ Hz, violet at 400 nm gives 7.5 × 10¹⁴ Hz.
The trap is the inversion: minimum frequency pairs with the LONGEST wavelength. Asked for the lowest visible frequency, reach for 700 nm, not 400 nm.
The trap
Pairing minimum frequency with minimum wavelength — f and λ run in opposite directions.
Prove it — watch it be true
- Slide the log-λ slider into the coloured visible band
- Park at 700 nm: f reads 4.3 × 10¹⁴ Hz at the red edge
- Park at 400 nm: f reads 7.5 × 10¹⁴ Hz — shortest λ, highest f