Question
Write down Huygen's principle and explain how a new plane wavefront is formed at the end of a very small time interval.
✓
Answer
• Huygen's principle :
→ "Every point or particle of a wavefront behaves as an independent secondary source, emits by itself secondary spherical waves. After a very small time interval the surface tangential to all such secondary spherical wavelets gives the position and shape of the new wavefront."
→A plane wavefront $F _1 F_2$ is shown in the fig. at time $t=0$.
→To determine the shape of the wavefront at time $t=\tau$, we draw spheres of radius $v \tau$, from each point (points $A _1, B_1, C _1 \ldots$ etc.) on the wavefront. (Where $v$ is the speed of waves in the medium.)
→A tangent common to all such points is drawn, which gives the position and shape of the new wavefront at time $t=\tau$.
→ "Every point or particle of a wavefront behaves as an independent secondary source, emits by itself secondary spherical waves. After a very small time interval the surface tangential to all such secondary spherical wavelets gives the position and shape of the new wavefront."
→A plane wavefront $F _1 F_2$ is shown in the fig. at time $t=0$.
→To determine the shape of the wavefront at time $t=\tau$, we draw spheres of radius $v \tau$, from each point (points $A _1, B_1, C _1 \ldots$ etc.) on the wavefront. (Where $v$ is the speed of waves in the medium.)
→A tangent common to all such points is drawn, which gives the position and shape of the new wavefront at time $t=\tau$.
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