I. Fill in the blanks. Choose the correct answer from the word pool.

Electromagnetic wave is a combination of ________________ and
_______________ field. It is produced by _____________ electrons. It has a speed
of _____________ like the speed of light and could travel through
_________________. EM waves differ in wavelength and frequency. Waves with
longer wavelengths have ___________ frequency and those that have shorter
wavelengths have _________ frequency and have the _________ energy. The
unit used to measure the frequency of a wave is _______________ and the
wavelength is expressed in ________________.