In a ripple tank, Hale sends straight ripples at a metal barrier. They arrive slanted, and they leave slanted the other way.
A reflected wave does not always go straight back along its arrival path. At what angle does it leave?
Angles at a boundary are measured from one reference line: the normal, the line perpendicular to the boundary.
Hale's ripples arrive at 30° from the normal.
They leave at 30° from the normal too, on the other side of it.
The two angles always match. Arrive at 50° from the normal, leave at 50°; arrive at 10°, leave at 10°.
One special case to know: a wave arriving along the normal itself leaves along the normal, straight back the way it came. The rope pulse bouncing off a wall is this case.
A straight ripple strikes a barrier at 30° from the normal. At what angle from the normal does it reflect, and on which side?
A reflected wave leaves at the same angle it arrived, measured from the normal.
It arrived at 30° from the normal.
It reflects at 30° from the normal, on the other side of the normal.
A ripple arrives at a straight barrier at 65° from the normal. Describe the reflected ripple's path.
The reflected angle matches the arrival angle, measured from the normal.
The reflected path sits on the other side of the normal from the arrival path.
The reflected ripple leaves at 65° from the normal, on the other side of the normal.
A straight ripple arrives at a barrier at 40° from the normal. Enter the angle, in degrees, between the reflected ripple's path and the normal.
From which line are a reflected wave's arrival and departure angles measured?
Eirik says: 'A wave that arrives at a barrier along the normal reflects straight back the way it came.' Is Eirik correct?
A water wave arrives at a straight harbor wall at 25° from the normal. Enter the angle, in degrees, between the reflected wave's path and the normal.
Griet measures an incoming ripple at 35° from the normal to a straight barrier. Which description gives the reflected ripple?
A pulse arrives head-on at a wall, traveling along the normal. Enter the angle, in degrees, between the reflected pulse's path and the normal.