Appearance of a Mysterious Reflection: What’s Going On Here?
Wherein my book becomes a strange mirror
Every once in a while I will notice something strange about my corner of the world and wonder what is the cause of it.
Now, I have a Ph.D. in physics, so I try to draw upon that ancient knowledge (because it has decades since I practiced) to explain away these curiosities. But this one had me going for a while.
Let’s see if you can figure it out faster than I could…
To begin our exploration of the mystery you must first be aware of the reality of a simple observation in the physical world. If you place a large mirror on the ground between you and a distant object you will notice something.
When viewed in the mirror the distant object appears to be inverted. This explains why the reflective surface of a still lake inverts the image of the landscape at the other end of it (as shown in the image above).
But let’s have a look at this on a very much smaller scale — inside my living room where we are going to find that the laws of physics appear to break down.
The following image shows the illuminated screen of my television (distant object) at night in a darkened room. Between the the television and myself is a piece of shiny (highly reflective) plexiglass lying flat on a pile of books on the table in front of me.
As expected, the image from the television is inverted in the plexiglass.
So far, so good. We understand intuitively (without stopping to go into the physics of it) what is going on.
Of course, when I am watching television at night I do not normally have a piece of shiny plastic sitting between me and my show. It would be too distracting.
But I do always have a pile of books on my table and recently I noticed something when I glanced down at the book closest to me. It happens to have a semi-glossy cover.
Look carefully. Can you spot the problem?
That’s right. The image is not inverted.
It is the right way up!
Admittedly there are a few things you have to take into account to confirm this:
● The reflected image from the cover is limited vertically in what it shows of the television screen. It corresponds to the center of the screen.● The cover of the book is not perfectly flat, so the image is wavy.● The semi-gloss nature of the cover smears the details of the reflection.
But if you look carefully you can see that for the image of the woman on the left, her hair descends and ends above her jacket as it should in a right-way-up image.
Likewise, although very smeared, you can see for the woman on the right her white sleeve is at the bottom of the image and her (very blurred) phone is above it.
Not convinced?
Here are a few more snaps for your brain to work on.
OK, Leonard. I believe you.
Your amateurish snapshots will not win any photographic contests, but I see your point. Something very strange going on with your book. Where did you get it?
Good question.
Is this odd kind of reflection a property of the book?
To find out I located another book in the pile which had a similar semi-glossy cover and positioned it behind the first book (so the new book cover is closer to the television).
Now we can compare reflections and see whether they are both non-inverting…
No. The new book cover is doing the opposite thing. It is showing an inverted television image, just as you would expect it to do.
Are you surprised by this? I was.
But wait. I know what must be going through your mind. The two books are at different distances from the television. Maybe this reflection voodoo is a property of distance.
So let’s check that. In the next set of images I have swapped the positions of the books. Has it made any difference to what we see going on?
Well look at that.
Now the inverted images are in the foreground and not the background. The ability to invert or not invert the image is shown to be a property of the cover of the book.
Uh-huh. Now we are getting somewhere…
So what could be the difference between these two book covers that explains the opposite laws of reflection?
Why does one cover invert the image as expected while the second cover appears to defy the laws of physics and shows the image the right way up?
I will give you the answer in the follow-up article to this one, where I will throw some physics at you. Admittedly very simple physics, but physics nonetheless.
So break out your genius hat, you’ll be needing it.
No, not really. The resolution to the mysterious nature of the reflections seen in my living room is not too difficult to explain.
But if you think you have it figured out already leave a comment before clicking on the link below and heading off to discover whether you were right or not.
Appearance of a Mysterious Reflection: What’s Going On Here? (Part II)
Other curious articles for you to consider, courtesy of Mr. Crane:
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