Describe how the wavelets that form in the wavefront apparently vanish behind it?
The phenomenon of wavelets apparently vanishing behind a wavefront can be explained using Huygens' principle. According to Huygens' principle, every point on a wavefront can be considered as a source of secondary spherical wavelets. These wavelets propagate in all directions from their respective points of origin.
When these wavelets reach the wavefront, they interfere with each other. At points where constructive interference occurs, the amplitude of the resulting wave becomes larger. However, at points where destructive interference occurs, the wavelets cancel each other out, resulting in a diminished or zero amplitude.
Now, let's focus on a point on the wavefront where the wavelets reach from behind the wavefront. Since the wavefront is already in front of this point, the incoming wavelets from behind will interfere with the forward-propagating wavelets.
At this particular point, if the wavelets from behind the wavefront interfere destructively with the forward-propagating wavelets, their amplitudes will cancel out, causing the wave to lose energy and appear as if it has vanished. This is the region behind the wavefront where the wavelets appear to vanish.
It's important to note that although these wavelets seemingly vanish behind the wavefront, they continue to propagate and interfere with the forward wave. The net effect is the diminishing of the amplitude of the wave behind the wavefront, creating the appearance of vanishing wavelets.