33. The electromagnetic spectrum includes all electromagnetic waves, from radio waves with long wavelengths and low frequencies to gamma rays with short wavelengths and high frequencies. Which statement best describes how fast these waves travel in a vacuum?

A : Gamma rays travel much faster than others because they have the highest frequencies.
B: All electromagnetic waves travel at the same speed.
C: High-frequency waves travel somewhat faster than low-frequency waves.
D: Infrared waves travel faster than ultraviolet waves.

Question

33. 	The electromagnetic spectrum includes all electromagnetic waves, from radio waves with long wavelengths and low frequencies to gamma rays with short wavelengths and high frequencies. Which statement best describes how fast these waves travel in a vacuum?
 	
	A : Gamma rays travel much faster than others because they have the highest frequencies.
	B: All electromagnetic waves travel at the same speed.
	C: High-frequency waves travel somewhat faster than low-frequency waves.
	D: Infrared waves travel faster than ultraviolet waves.

fuzzybird · Answer

@Michele_Laino @pooja195

plainntall · Answer

What do we know about electromagnetic waves travelling in a vacuum?
Read your book or look it up in wikipedia or a search engine "speed of electromagnetic waves in a vacuum", but you can also figure it out from the hints they give you.

We know that the speed of an electromagnetic wave is give by
$$v _{light}=c=wavelength \times frequency = \lambda \times \nu$$
We are told that for radio wave the wavelength is big but the frequency is small for gama rays when the wavelength is small, the frequency is big.  What does that suggest about the value of the speed of light in a vacuum?