State Huygens' principle of diffraction of light.

Explanation

**Step-by-Step Solution:**

1. **Understanding Huygens' Principle:**
Huygens' Principle states that every point on a wavefront can be considered as a source of secondary wavelets. This means that each point on the wavefront emits its own wavelet, which spreads out in the forward direction.

2. **Formation of New Wavefront:**
The new wavefront at a later time can be constructed by considering the envelope of these secondary wavelets. The new wavefront is formed by the combination of all the secondary wavelets emitted from the points on the original wavefront.

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