IPA: /ˌmʌltiˈweɪv.lɛŋθ/
KK: /mʌltiˈweɪv.lɛŋkθ/
Relating to or using several different wavelengths of light or other electromagnetic radiation.
The multiwavelength observations provided a clearer picture of the astronomical event.
Multiwavelength → It is formed from "multi-" (meaning many) and "wavelength" (from the combination of "wave" (from Old English *wafian*, meaning to wave) and "length" (from Old English *length*, meaning the measurement of something). The word refers to many different wavelengths of light or other electromagnetic radiation.
Think of 'many' ('multi-') types of 'waves' ('wave') measured by their 'length' — that's what multiwavelength means.
No commonly confused words.