How are electromagnetic waves and mechanical waves alike?
They are almost the same. Mechanical waves contain crests and troughs of displacement .. i.e., a crest when displacement is highest in the positive direction and trough when displacement is highest in negative direction. So, the displacement reaches highest, goes to 0 and then highest in negative direction and back to 0, etc … this is a mechanical wave. In electromagnetic waves, the electric field value is the one that oscillates. It reaches a maximum, comes back to 0, reaches maximum in the other direction and then back to 0. In both cases, the wave is expressed as a sine/cosine function multiplied with its amplitude (the maximum value in either direction). y = A sin (wt + a) … mechanical E = E0 sin (wt + a) … electromagnetic One major difference between the two is probably that though mechanical wave is just displacement, electromagnetic wave is a combination of 2 waves .. one is electrical where electric field E varies sinusoidally and other is magnetic where magnetic field B
(1) Both EM and mechanical waves rely on two forms of energy storage; energy is continually converted from one to the other and back again as the wave propagates. For mechanical waves, they are kinetic and potential energy (as movement of mass and elastic deformation of solid/liquid/gas). For EM waves, they are the energy of electrostatic and magnetic fields. (2) Both EM and mechanical waves have a fixed velocity in a particular medium (not entirely true for mechanical waves or EM waves not in space, where velocity can vary with frequency). (3) Both EM and mechanical waves have a frequency and a wavelength. The wavelength is the velocity divided by the frequency. (4) Both EM and mechanical waves can carry energy from one A to B without anything except the wave physically moving from A to B.
