Describe how the wavelets that form in the wavefront apparently vanish behind it?
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Actually to explain the energy propagated by a wave , ther is a proposed obliqiuty factor ,1+cos(theta)=q .
In the case when the backward wavefront is taken the angle becomes 180degrees and as a result q= 0 , it means no energy propagation in the backward direction.
When waves travel through a medium, such as water or air, they create a disturbance that spreads out in all directions. This disturbance is known as a wavefront. One interesting phenomenon that occurs with waves is the apparent disappearance of wavelets behind the wavefront.
To understand this, imagine dropping a rock into a calm pool of water. As the rock hits the water, it creates a circular wavefront that expands outward. If you observe this ripple pattern, you might notice that as each individual wavelet reaches the wavefront, it seems to vanish or disappear.
This phenomenon can be explained by the principle of interference. Interference occurs when two or more waves overlap and combine, resulting in either reinforcement (constructive interference) or cancellation (destructive interference) of the wave amplitudes. In the case of the wavelets behind the wavefront, they experience destructive interference.
Destructive interference happens when two waves overlap and their amplitudes are out of phase. In other words, the crest of one wave meets the trough of the other wave, causing the two waves to cancel each other out. As a result, the wavelets appear to vanish behind the wavefront.
If you want to see this phenomenon in action, you can conduct a simple experiment. You can create ripples in a container of water and observe how the wavelets seemingly disappear as they reach the edge of the container. This demonstrates how destructive interference can cause the wavelets to vanish behind the wavefront.