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.
By placing two mirrors at a 90-degree angle to each other, you can create a reflection that allows you to see the back of your head. This is similar to how a periscope works, which uses multiple mirrors to reflect light and change the direction of the image.