[问答题]
State Huygen's princl+9 r - .4nnlb f cba;nmghnvjj77(:mppd p+yh-,iw:x iple.
参考答案: Every point on a wave front can be considered as a source of tiny wavelets that spread out in the forward direction at the speed of the wave itself. The new wave front is the envelope of all the wavelets - that is, tangent to all of them.
