CHAPTER 15. EM RADIATION 15.4
Exercise 15 - 2
- List one source of electromagnetic waves. Hint: consider the spectrum diagram
and look at the names we give to different wavelengths. - Explain how an EM wave propagates, with theaid of a diagram.
- What is the speed of light? What symbol isused to refer to the speed of light?
Does the speed of lightchange? - Do EM waves need amedium to travel through?
More practice video solutions or help at http://www.everythingscience.co.za(1.) 01m4 (2.) 01m5 (3.) 01m6 (4.) 01m7The radiation can take on any wavelength, which means that the spectrum is continu-
ous. Physicists broke down this continuous bandinto sections. Each section is defined
by how the radiation is created, not the wavelength of the radiation. But each category
is continuous within themin and max wavelength of that category, meaning there are
no wavelengths excluded within some range.
The spectrum is in order of wavelength, with the shortest wavelength at one end and
the longest wavelengthat the other. The spectrum is then broken downinto categories
as detailed in Table 15.1.
Table 15.1: Electromagnetic spectrum
Category Range of Wavelengths (nm) Range of Frequencies (Hz)
gamma rays < 1 > 3 × 1019
X-rays 1-10 3 × 1017 - 3 × 1019
ultraviolet light 10-400 7 , 5 × 1014 - 3 × 1017
visible light 400-700 4 , 3 × 1014 - 7 , 5 × 1014
infrared 700- 105 3 × 1012 - 4 , 3 × 1019
microwave 105 − 108 3 × 109 - 3 × 1012
radio waves > 108 < 3 × 109Since an electromagnetic wave is still a wave, the equation that you learnt in Grade 10
still applies: c = f· λ.