22_emr - Lesson 22: Electromagnetic Radiation...

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Lesson 22: Electromagnetic Radiation Electromagnetic radiation is a way that energy can be transferred. It is special in that it is made up of alternating, perpendicular electric and magnetic fields. These alternating fields essentially act as transverse waves traveling outwards from their source. That's where the “radiation” part comes from. .. they radiate outwards in all directions. EMR (as electromagnetic radiation is often referred to) travels at an incredibly high velocity of 3.00e8m/s. The form of EMR that most people easily recognize is visible light, so we often refer to this velocity simply as the speed of light. Always remember that this velocity refers to all forms of EMR, not just visible light. Although all EMR has the same velocity, the different kinds all have their own distinct sources , frequencies , and wavelengths . The different sources all involve accelerating charges of some sort, which is the cause of the electric and magnetic fields. The EMR can be detected either. .. Directly , if it travels directly from the source to the observer. e.g. looking at a fire. Indirectly , reflected from a surface or transmitted through a substance. e.g. visible light from a lamp is reflected off a page of a book to your eyes. e.g. sunlight is transmitted through a window, When we start to look at EMR, we often look at it as a spectrum . You are already used to looking at the spectrum of visible light, probably by remembering the order of the colors of the rainbow using ROY G BIV. Visible light is actually a very small part of the entire EMR spectrum. EMR Spectrum The EMR spectrum starts with very low frequencies, and goes up to higher and higher frequencies. This means that the wavelengths are getting smaller and smaller.
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22_emr - Lesson 22: Electromagnetic Radiation...

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