Which WiFi frequency has the longest wavelength?

So the wavelength is: 671nm (red light) .

Frequency – Wavelength Chart FrequencyWavelength1/100 Wavelength3.0 GHz10 cm1.0 mm4.0 GHz7.5 cm0.75 mm5.0 GHz6.0 cm0.6 mm10 GHz3.0 cm0.3 mmFrequency – Wavelength Chart www.hottconsultants.com › techtips › freq-wavelength

Use 2.4 GHz for a device farther from the router This wavelength has a longer range and can penetrate solid objects more easily than the 5 GHz band, making it ideal for devices that are taken from room to room or are more distant from the router.