According to huygens's principle, what is the explanation for boundary behaviors?

a.) each point on a wave front acts as a source of secondary waves.

b.) each point on a wave front stops moving as it progresses.

c.) each point on a wave front partly reflects and partly refracts the wave.

d.) most of the points on the wave front stop progressing.

A.) Each point on a wave front acts as a source of secondary waves.

Explanation:

Huygen's principle can explain some phenomena such as the diffraction of light through a single or a double slit, and the interference pattern that we see on the screen. In fact, according to Huygen's principle, each point of the wave front inside the gap in the slit acts as a source of secondary waves: therefore, we can imagine all the points inside the slit as sources of secondary waves, and these waves interact with each other producing interference, and this is why we observe an interference pattern on the screen.