Consider again the periodic variation of temperature in a semi-infinite domain analyzed. Sketch or plot the temperature for three values of time. Show that a wave type of propagation of the temperature is observed. Find the distance between adjacent maxima in the temperature at any given instant of time (which is called the wavelength).

Also find the speed of propagation of the thermal waves. This is defined as the distance between two adjacent peaks divided by the time needed for the crest to travel this distance.