Select the correct mirror image of the given figure when the mirror is placed…

Concept — a right-side mirror reverses one axis only. A mirror standing along the right edge reflects the drawing across a vertical axis, so the horizontal order is turned around and every horizontal direction is reversed, while vertical positions and up-down orientation stay exactly as they are. Two consequences follow:

• whatever lay furthest to the left in the original lies furthest to the right in the reflection, and an arrow that pointed one way now points the other way;

• a part that is already symmetric about a vertical axis reproduces itself unchanged, and object properties such as shading, fill and line thickness are copied exactly, because they describe the object rather than its orientation.

Application. Read the given drawing from left to right: a tall unfilled bar; two block arrows leaving the bar's right edge and pointing right; and an open bracket whose flat edge runs along the bottom, with an inner zigzag dipping to a trough on that bottom edge. Reflecting it in a mirror held along the right edge takes four steps:

1. Turn the horizontal order around, so the open bracket stands leftmost, the two block arrows in the middle and the tall bar rightmost.

2. Reverse every horizontal direction, so the two block arrows now leave the bar's left edge and point left, towards the bracket.

3. Leave the vertical axis untouched, so the bracket keeps its flat edge along the bottom and its inner zigzag still dips to a trough on that bottom edge.

4. Copy the object properties unchanged, so the tall bar remains unfilled.

The reflection is therefore an unfilled tall bar on the right, two block arrows on its left edge pointing left, and the open bracket on the left with its flat edge along the bottom and the inner zigzag dipping to a trough.

Cross-check. Set that result against the other configurations drawn here:

• keeping the tall bar on the left with the two block arrows pointing right leaves the horizontal order and the arrow direction as they were, so no lateral reflection has taken place;

• moving the bracket's flat edge to the top so that the inner zigzag rises to a peak is a turn about a horizontal axis, which yields the water image rather than a right-side mirror image;

• filling the tall bar solid black alters a property of the object itself, and reflection copies shading exactly.

Reflecting the chosen drawing once more should give back the original drawing, and that reversibility is the quickest confirmation.