How does the width of the visible spectrum compare to the entire electromagnetic spectrum?

Answer 1

it is slap bang in the midde of the spectrum, with Ultra Violet light on one side, and Infra red on the other. In a vacuum it travels at the same speed as all of the others (the speed of light) UV has a shorter wavelength, and Infra red has a slightly longer one.

Answer 2

It is very short compared to the whole length of the EM spectrum.

===============================================

Another contributor rushed in where the first feared to tread:

First of all ... there's no such thing as the "entire electromagnetic spectrum". If you

name a frequency, then no matter how low it is, I can always name one lower ... and

probably generate it with some simple electronics. And no matter how high it is, I can

name one higher, whether or not it's ever been observed in nature yet. So we'll need to

choose some limits for what we mean by "entire electromagnetic spectrum".

One source we found quoted the highest observed gamma-ray frequency as 1022 Hz, so

let's use that as an upper limit. For a lower limit, let's use the lowest audio frequency that

usually appears on a specification for a home stereo or a set of earphones ... 20 Hz.

For the visible spectrum, we'll use 380 to 790 THz, = (3.8 to 7.9) x 1014 Hz ... a bandwidth

of 4.1 x 1014 Hz, or 61% of one decade, or 2.04 octaves. (You could look it up.)

OK. I think we're set up to answer the question now:

Linearly (arithmetically):

Visible spectrum as a fraction of total spectrum = (4.1 x 1014) / (1022) = 0.00004 %

Logarithmically: (0.61 decade) / (20.7 decades) = 2.9 %