Which of the answer figures is the exact mirror image of the given problem…
2023
Which of the answer figures is the exact mirror image of the given problem figure when the mirror is held at the right side?
Problem Figure:
Attempted by 18 students.
Show answer & explanation
Concept: A mirror placed along the right-hand edge produces a lateral inversion, that is a reflection across a vertical axis. Every element keeps its height and its own shape, but its horizontal side is exchanged: whatever lies towards the left of the original moves towards the right of the image, and whatever lies towards the right moves towards the left. Vertical order never changes, nothing is rotated, and lettering is reversed rather than left readable.
Application: The given figure is a square frame holding four corner groups of triangles arranged around the lettering BE. Applying the vertical-axis reflection group by group gives the following requirements for the image.
The pair of small triangles along the top reads hollow on the left and solid on the right, so in the image it must read solid on the left and hollow on the right, both still pointing upward.
The pair of large downward triangles just below reads solid on the left and hollow on the right, so in the image it must read hollow on the left and solid on the right.
The pair of large upward triangles lower down reads solid on the left and hollow on the right, so in the image it must read hollow on the left and solid on the right.
The pair of small triangles along the bottom reads hollow on the left and solid on the right, so in the image it must read solid on the left and hollow on the right, both still pointing downward.
The lettering BE sits to the right of centre and reads normally, so in the image it moves to the left of centre and each letter is itself reversed, the reversed E standing before the reversed B.
Cross-check: The required answer figure is the one that meets all five requirements together, namely solid-then-hollow small triangles along the top, hollow-then-solid large triangles in both the upper and the lower pair, solid-then-hollow small triangles along the bottom, and reversed lettering placed to the left of centre. An answer figure that reproduces the given arrangement unchanged meets none of them, because a mirror image is never identical to a figure that is not itself left-right symmetric. An answer figure that reverses the top rows and the lettering but keeps the bottom pair of small triangles shaded as in the given figure misses the fourth requirement. An answer figure whose lettering is still readable misses the fifth requirement outright, since lateral inversion always reverses text.