Huygens’ Principle
Each point along the initial vertical line acts as a
secondary source that emits circular wavelets.
The green curve shows the
outer envelope of these wavelets — this represents the position of the wavefront as it propagates.
[
please not that this is not a true physical model of Huygens' principle, and is for illustrative purposes only]
👉
Activity:
Start with a single point source and observe the circular wavefront.
Now gradually increase the number of points from
1 to 21.
➡ As you increase the number of sources:
- The individual circular wavelets begin to overlap
- The outer envelope becomes smoother
- The wavefront approaches a straight line (a plane wave)
This demonstrates how a plane wave emerges from many simple point sources.
Effect of Frequency
The frequency slider controls how often new wavefronts are produced.
👉 Increase the frequency and observe:
- The spacing between successive wavefronts decreases
- The wavelength becomes shorter
Lower frequencies produce widely spaced wavefronts, while higher frequencies produce more closely spaced wavefronts.
Effect of Speed
The speed slider controls how quickly each wavelet expands.
👉 Increase the speed and observe:
- Wavefronts travel faster across the screen
- The spacing between wavefronts increases for a fixed frequency
- The wavelength becomes longer
Decreasing the speed slows the propagation and reduces the wavelength.