This is a still capture of a water wave.

Blue text identifies physical objects.

Red text shows the motion of waves.

Green text indicates the measurements needed.

Notice that the original wave front, while traveling to the right, is vertically oriented (just like the direction of motion of the reflected wave).  The reflected wave front is horizontally oriented (just the original wave's direction of motion) but travels upwards.

When you measure an angle of incidence and an angle or reflection or refraction. Remember:

The angle is measured by referencing the direction of wave motion (not the direction of the wave front) with a line perpendicular to the barrier.

Why is this so important?
You won't easily discover any rules for wave behavior unless you use this measurement system!