Greer stands 3 m from her bedroom mirror and takes one big step toward it. Her image does not wait: it moves too. How far did it move, and which way?
You know the rule: a plane mirror's image is as far behind the mirror as the object is in front. This lesson uses the rule as a moving tool: when the object moves, the image keeps the match.
Greer starts 3 m in front of the mirror, so her image starts 3 m behind it.
She steps 1 m closer, to 2 m in front.
The image must stay as far behind as she is in front, so it moves to 2 m behind.
Step away, and the image steps away by the same amount.
The image never slides onto the glass and never sits on it: it keeps the matched distance behind the mirror.
Size does not change either: the image stays the same size as the object, near or far.
It can look bigger as you walk closer, because it is nearer to your eye; its actual size stays yours.
Fintan's dog sits 2.2 m in front of a plane mirror, then walks 0.4 m toward it. Where is the dog's image now?
The dog is now 2.2 − 0.4 = 1.8 m in front of the mirror.
The image stays as far behind the mirror as the dog is in front.
The image is now 1.8 m behind the mirror.
A parakeet hops 0.3 m away from a plane mirror, starting 0.9 m in front. Which way does its image move, and to where?
The parakeet is now 0.9 + 0.3 = 1.2 m in front.
The image keeps the match, so it moves to 1.2 m behind the mirror.
It moved 0.3 m farther from the mirror, matching the hop.
The image moves 0.3 m away from the mirror, to 1.2 m behind it.
Haldis walks toward a plane mirror. What does her image do?
A cat sits 2.5 m in front of a plane mirror, then creeps 1 m closer. Enter the distance, in m, from the mirror to the cat's image now.
Fintan walks 0.5 m toward a plane mirror. He says his image also moves 0.5 m toward the mirror. Is Fintan correct?
A robot vacuum backs 0.9 m away from a hallway's plane mirror. What does its image do?
Elowen stands 6 m from a plane mirror and walks 2.5 m toward it. Enter the distance, in m, from the mirror to her image now.
Greer backs slowly away from a plane mirror while watching her image. Which statement describes the image during her walk?