70981

IIIustration of solution

We chose for our first illustration the situation when only a forward wave is present. The

wave may be illustrated against a time axis as shown in Figurę 2.4. Because the function

Vfis of the single argument z - ct, if the voltage observed at the origin of position as a

function of time is represented by the solid curve in Figurę 2.4, then at some position to

the right of the origin the same voltage as a function of time will be observed but at a later

time, as is shown by the dotted curve. As the observation point is moved progressively

to the right to larger values of the position coordinate z, there will be an increase in the

delay before the above defined voltage waveform is observed. Ali of these features are illustrated in Figurę 2.4.

The situation on the linę may alternatively be represented as shown in Figurę 2.5,

wherein at one particular time the voltage waveform for all points on the linę is shown.

This illustration is for a wave of the same shape as was illustrated in Figurę 2.4. If one

pictures the wave at later and later times, it will be seen to have moved further and

further to the right.

It is interesting to notę the shape of the wave in this latter diagram appears to be a

mirror image of the one when drawn against the time axis. This is a natural consequence

of the fact that the shape of the forward wave is an expressed as a function Vfof the

single argument z - ctand the coefficients of z and t in that combination have

different

signs.