Outside a harbor, the sea arrives as long straight waves. Inside, behind the narrow opening in the harbor wall, boats bob on waves that sweep in arcs across the whole basin.
The opening faces straight out to sea, yet the waves inside reach every corner, including spots nowhere near the straight-through line. What happened at the opening?
Send a wave at a gap in a barrier, and it does not simply continue as a straight band the width of the gap.
Past the gap, the wavefronts swing wide at their ends and travel outward in arcs. The wave spreads into the space beyond, reaching places a straight-line path would miss.
Edges do it too. A wave passing the end of an obstacle spreads around that end, into the region behind the obstacle.
Diffraction changes none of the wave's measurements. The medium is the same, so the speed is unchanged; the source is the same, so the frequency is unchanged; and the spacing between fronts stays one wavelength.
Only the travel direction fans out: one incoming direction becomes a spread of directions.
Straight ripples pass through a gap between two barriers in a ripple tank. What shape are the ripples beyond the gap, and what happens to their wavelength?
Beyond the gap, the fronts swing wide at their ends and travel outward in arcs.
The medium and the source are unchanged, so the front spacing stays one wavelength.
The ripples spread out in arcs beyond the gap; their wavelength is unchanged.
Straight ripples pass the end of a low wall that sticks out into a pond. What happens in the water behind the wall?
The wall's end is an edge, and a wave passing an edge spreads around it.
The ripples curl into the region behind the wall, which a straight-line path would never reach.
The ripples diffract: they spread around the wall's end into the water behind it.
Straight ripples reach a gap between two barriers in a ripple tank. What do the ripples do beyond the gap?
Griet says: 'A wave that passes the edge of an obstacle spreads into the region behind it.' Is Griet correct?
A wave passes through a gap and spreads out beyond it. What is this spreading called?
Straight water waves diffract through a gap in a harbor wall. Which statement about the waves beyond the gap is correct?
A low wall sticks out into a lake, and straight ripples pass its end. What happens in the water behind the wall?
Which case shows diffraction?