Electromagnetic waves are often described as self-sustaining oscillations of electric and magnetic fields that do not require a material medium.
a. (i) Describe, in logical steps, how a time-varying electric field gives rise to a magnetic field and how the resulting magnetic field in turn produces an electric field.
b. (ii) Illustrate the relative orientations of the electric field, magnetic field and direction of propagation for a plane electromagnetic wave travelling in free space.
c. (iii) Explain why such a mechanism allows electromagnetic waves to propagate through vacuum, whereas mechanical waves like sound cannot.