The object (you) is represented by the arrow on the left - your eye is the dot near the top. You can click-and-drag on the dot at the bottom of the arrow to move the object left or right.

You have a height h. What is the minimum height possible for a plane mirror so that you can see your entire reflection in it without moving your head?

1. h
2. smaller than h but larger than h/2
3. h/2
4. smaller than h/2
5. it depends on how far you stand from the mirror

No matter how far you are from the mirror, the minimum height necessary is h/2. The mirror has to be positioned just right, though.

At what height should the very top of the mirror be placed?

1. even with the top of your head
2. halfway between the top of your head and your eye level
3. at your eye level
4. below your eye level
5. it depends on how far you stand from the mirror

The top of the mirror should be at a height halfway between the top of your head and eye level. That's the point on the mirror a ray of light from the top of your head reflects off on its way to entering your eye. Similarly, the bottom of the mirror should be at a height equal to half the distance between your eyes and the floor.