1pt An ocean wave encounters a narrow slit. After it travels through the slit, it spreads out radially. What is this called?

Diffraction

Explanation:

Diffraction is a phenomenon typical of waves.

Diffraction occurs when a wave passes through a narrow slit, when it encounters an obstacle: in this situation, the wave passes through the slit (or bends around the obstacle), and its wavefronts, initially parallel to each other (wavefronts are lines connecting all the points in phase along the wave), become circular after the slit / obstacle.

This phenomenon occurs because each point inside the slit acts as a new source of the wave, producing circular waves after the slit. As a result, waves produced by each point along the slit produce interference with the waves from the other slits, so there will be points with constructive interference (where the amplitude of the waves add up together) and points with destructive interference (where the amplitude of the waves cancel out).

It is worth noticing that diffraction occurs only when the wavelength of the incoming wave is of similar size as the width of the slit, or with the size of the obstacle. If the slit is too large, the wave passes through it without producing diffraction.