Final answer:
To see the back of your head, you can use two mirrors arranged at a 90-degree angle. The height of a mirror needed to see your entire body in it is equal to your total height. The size of a mirror does not affect the height of your reflection.
Step-by-step explanation:
To see the back of your head, you can use a set of two mirrors arranged at a 90-degree angle. When the mirrors are positioned correctly, you will be able to see the reflection of the back of your head in the second mirror. Therefore, the minimum number of mirrors needed for this task is two.
If you wish to see your entire body in a flat mirror from head to toe, the height of the mirror should be equal to your total height. The size of the mirror does not depend on your distance away from it; as long as the mirror is tall enough to reflect your entire body, you will see yourself from head to toe.
In the case of a flat mirror, the size of the mirror does not affect the height of your reflection. The mirror only reflects the light that reaches it, so its size does not determine the size or height of your reflection.