Walking backwards away from a mirror, Nilesh says his image stays exactly his own size — it only…
Walking backwards away from a mirror, Nilesh says his image stays exactly his own size — it only looks smaller from far away, the way a real person standing far off looks smaller. Hemant says the image really does shrink as you step back from a mirror — you can clearly see it getting smaller. Whose reasoning holds up?
Who do you think is right? Pick one.
The answer: Nilesh is right, a plane mirror's image is the same size as the object
Why
Hemant is reporting what he truly sees — the image does look smaller — so his observation is honest. The question is why. When Nilesh steps back 1 m, his image also moves 1 m further behind the mirror, so the image ends up 2 m further from his eyes. Anything further from your eyes looks smaller, whether it is an image or a real bus down the road. The image itself stays the same size as Nilesh: a plane mirror always forms an image that is the same size as the object, upright, and as far behind the mirror as the object is in front of it. Test: ask a friend to stand behind you, as far from you as your image is — your friend looks just as small as your image does, yet nobody thinks your friend has actually shrunk. Nilesh is right: the image in a plane mirror stays the same size as he is; it only looks smaller because it is further from his eyes.
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