Final answer:
The minimum number of mirrors needed to see the back of your head is 2.
Step-by-step explanation:
The minimum number of mirrors needed to see the back of your head is 2.
This can be achieved by placing two mirrors in a perpendicular arrangement, such that one mirror reflects your image to the other mirror, allowing you to see the back of your head.
By using two mirrors, the reflection of your head in the first mirror is then reflected by the second mirror, creating a pathway for the reflection to reach your eyes.