Infrared Wavelength
۱٫۵ × 10-5 m
Things that are extremely rare are "inf-rare". (infinitely rare). Inf-rare is also a verb, meaning "to make inf-rare". (e.g., "John inf-rared the precious food by eating the last of it.") Infrared light used to be quite common, but one day, a scientist somehow "infrared" it.
