Electromagnetic Radiation

Note: This page refers to the lecture in PH1011, not the phenomena itself.

Previous: N/A

Next: What is Light, and How is it Generated?

Electromagnetic Radiation is the first lecture within the Waves and Optics section of PH1011. It is an introduction to EM radiation - namely what light is and how it occurs.

Definition of light
Light refers to visible EM radiation - wavelengths which occur between 400 and 700nm. They arise through a combination of perpendicular electrical and magnetic fields; a changing electrical field induces an in-phase changing magnetic field and vise versa, and the elecromagnetic field arises here. However the two parent fields do not form each other - they keep inducing new fields, indefinitely.

Source
The fields are created by the motion of an oscillating charge; accelerating charged particles causes the release of EM waves, which in this case include visible wavelengths. Field lines flow from positive to negative charges in an electric field, and as with all waves the wavespeed is given by v = fλ. All light waves travel at equal speed, c, so if the frequency or wavelength of an individual wave is known then the other can be calculated.

Summary
The electromagnetic spectrum is a series of waves which travel with equal speed in a vacuum, induced by the acceleration of charges in an EM field. The human eye can detect some of these wavelengths and interpret them as light.

|Reference 1

|Reference 2