b band blue c band d band e band electromagnetic spectrum extremely high frequency extremely low frequency f band g band gamma ray green h band hertz high frequency i band infrared k band l band longwave low frequency m band medium frequency medium wave microwave q band radar radio frequency radio waves red s band shortwave super high frequency super low frequency technology terahertz radiation ultra high frequency ultra low frequency ultraviolet v band very high frequency very low frequency visible spectrum w band wavelength wireless x-ray x band yellow