Which statement is true about the speed of waves in the electromagnetic spectrum?
a) the speed of all electromagnetic wave is inversely proportional to their wavelength.
b) the speed of all electromagnetic waves is directly proportional to their frequency.
c) in a vacuum, all electromagnetic waves travel at speeds between 1.098 x10^5 and 2.998 x 10^8 m/s.
d) in a vacuum, all electromagnetic waves travel at the peed of 2.998 x 10^8 m/s.