Why mirrors seem to swap left and right only

Question

A mirror seems to switch left and right, yet it does not appear to turn things upside down. Explain why.

Short answer

A mirror actually reverses front and back, not left and right. Points are reflected only along the axis perpendicular to the glass. We describe the image as left-right swapped because we compare it with a real person who turned around a vertical axis to face us; had they flipped over a horizontal axis, we would call it an up-down swap instead.

Adapted from Crack, Heard on the Street, Q1.58, p.20; question and answer rewritten by SelfMadeQuant.com.

See the hint and the full worked solution in the question bank (free account).

Open the worked solution

Lessons behind this question

Interest Rate Swaps: Mechanics, Valuation, and the Comparative-Advantage Argument

Start with a free lesson: Swaps is part of a free topic. Create a free account, no card needed, to read it in full with worked solutions.

Read it free