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Close Shave

Science brain teasers require understanding of the physical or biological world and the laws that govern it.


Puzzle ID:#36934
Fun:*** (3)
Difficulty:** (1.52)
Submitted By:drussel3*us****




Homer had suffered a bizarre accident that affected his eyesight. The doctor said it would be temporary, but for the next 4 weeks, he had to adjust how he did some things. The accident had affected his focal length. He was only able to focus on objects that were 6 or more feet away from him, anything closer than 6 feet was just a blur.

Homer was used to shaving up close in front of his bathroom mirror. Now after the accident, how close could Homer get to the mirror to see his face clearly enough to shave?

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Jun 14, 2007

Very interesting bit of trivia! I may have to try that when I get home!! Nice job!
Jun 14, 2007

By the way, I will try the tape thing, not the shaving thing...
Jun 14, 2007

That was easy. I've often thought about a mirror and depth, so it took me no effort, but it was a good teaser. 1 full star! √
Jun 15, 2007

haha i will try that!!
good one!!
Jun 15, 2007

I got it right away, but it was an awesome teaser! 1 full star from me too!
Jun 15, 2007

Quick question, I am new and want to earn points fast so I can do more stuff like submit my own teasers. How do I earn more points? Thanks again for the awesome teaser!
Jun 15, 2007

For points, you rate teasers. I points per teaser. And your account needs to be 5 days old and with 250 points to submit a teaser, then you work yourself up from their. Look at the FAQs.
Jun 16, 2007

cool, I tested it by holding a book up next to my head...the words were too small to read.
Jun 16, 2007

Thanks Kamzar! Will do!
Jun 16, 2007

Thank you too Kazamar. I only have 44 points and I too want to be able to do stuff on the site. thanks!
Jun 18, 2007

Jun 18, 2007

It was very easy, but also very fun. An aside note: Did you ever try stereographs (AKA 3D pictures)? Because they use the same concept: in order for the 3D picture to pop out, you need to be focusing as if you were looking at an object that is twice as far as the picture you are looking at (which takes some time to get used to). This is why some people find it easier to print the stereograph on glossy paper and focus on their reflection, which is twice as far as the picture. Try googling stereographs-they are very cool.
Jun 21, 2007

This would be great for kids in a science class to try. The comment about using glossy paper for stereographs is cool!
Jul 15, 2007


Jul 15, 2007

that answer for me was ...a million miles away.... im not a mathie....gimme some spelling bees...
Jul 15, 2007

Great teaser! I went off in the wrong direction and tried to set up an arrangement of multiple mirrors!
Jul 15, 2007

i had the answer but then thought there was a twist somewhere till i saw it was meant to be easy !

i need to checkout the stereographs next !

Jul 15, 2007

Very neat! I got it right, but not because of how the answer was to be attained! Oh well, very good!
Jul 15, 2007

You would have a hard time finding one any easier
Jul 15, 2007

Fascinating. I'll try this experiment also.
Jul 15, 2007

I had no clue Learned something though.
Jul 15, 2007

guess ya either know this stuff or ya don't.
Jul 15, 2007

nice and easy teaser.
Jul 15, 2007

To all the geniuses who think this was easy there are a few of us who
didn'texcel in science. I will look
up stereograhs & mayble learn

I don't ever want to be a know it all.

Thanks for sending this in
Jul 15, 2007

fun teaser you dont have to be a genied to figure it out
Jul 15, 2007

Well I guess I'm an idiot then, cause I missed it. Of course I've been out of school for 30 years. Maybe I'll get the next one. Thanks for the post.

Jul 15, 2007

That was an awesome Teaser. Glad it got picked as Teaser Of The Day. I guessed the right answer. I guess I missed that day in school (no surprise there), so it was nice to hear why it was three feet from the mirror. Keep 'em comin'!

~Insane Shelton
Jul 15, 2007

Ilearned something. It was nice Thx.
Jul 15, 2007

me too

i figured it was around 3 feet because you dont necessarily need crystal-clear vision to shave....but i had no idea that that's y.

very very cool!
Jul 15, 2007

Jul 15, 2007

Sorry, I found this one far, far too basic. The only thing that tricked me was its simplicity, I spent about 5 minutes re-reading the puzzle, looking for the catch, thinking "it couldn't be the obvious answer, could it?"
Jul 15, 2007

awesome. glad i finially got one. didn't take me long either.
Jul 16, 2007

Although to some this might be easy, it was in fact a very interesting fact that many people don't know. So don't feel dishartened by the negative comments. I have some extra things people might like to think about regarding mirrors. When you look in a convex mirror (such as a car mirror) do the images in it look further away or smaller? Also when you look through a pair of binoculars do images look closer or bigger? The answer is not both. CLUE - Think about the point where your eyes are focusing in each case and how the light rays travel in each system (A pair of binoculars have more than one lens (or mirror) and a car mirror, obviously only has only focus, which in the case of a convex mirror is behind it's surface)
Jul 16, 2007

Sorry! I made a tipo, In the above post "only has only focus" should read "only has one focus"
Jul 19, 2007

nice i never new tht
Jul 29, 2007

this was so easy though, it is basically common sense. geez...... (as Americans say)
Sep 16, 2007

Sep 21, 2007

Neat idea for a teaser, and nice to teach people new stuff with the answer.

I don't agree with the first sentence in the explanation of the answer, though. The concept of "focal length" has a very specific meaning that isn't quite the same as what was meant, although most laypersons wouldn't notice the difference. A change of wording such as this might be more appropriate:
"When looking at your reflection in a mirror, your eyes focus to a distance equal to your distance from the mirror plus the apparent distance that your reflection is from the mirror. In a flat mirror, the image is the same distance away from the mirror as the object that is reflected. So when standing three feet away from the mirror, and focusing on your face which appears to be three feet past the mirror, you are focusing at a distance of six feet."

I'm too lazy to figure out where to email this proposed correction, and I don't have enough points to correct it myself. Guess I need to submit some teasers, eh?
Jan 31, 2008

quite easy
Jul 15, 2010

Thanks for the posting. It made me aware of something I don't usually think about. As for the comments from previous years stating how easy/elementary this was, 1) I'm not a scientist, esp. not physics; 2) I skipped 5th grade; maybe that's where you all studied mirrors!! Always happy to learn new things.
Jul 15, 2010

I never learned this in school. I thought it was hard, but I knew the answer would be less than 6 ft., just didn't understand the science behind it. Verrrry interesting.
Jul 15, 2010

Qrystal's explanation of the answer (above) is definitely superior. Easy but fun teaser.
Mar 09, 2011

I dont really want to be negative but these are just way too easy! Could someone please come up with something a little higher than primary school level?
Jul 28, 2012

i got that correct
Jul 15, 2013

I do not think it was primary school level like some have said, but the very fact the question was asked, I knew t it was obvious.
Jul 15, 2013

Interesting teaser! Thanks for posting!
Jul 15, 2013

I'm sure the editors have put the teasers in the mirror. Every time they look they see the same old teasers. What a shame when there is new material available. There used to be many daily remarks, now you can count them one hand.
Jul 15, 2013

I think he should have grown a beard.
Jul 15, 2013

Nice Teaser even though it was quite easy. By the way, your explanation is much more simply stated than Qrystal's. If this is a grade school level teaser as many have said, then your explanation is better! Thanks for submitting!
Jul 15, 2013

Easy teaser. but you can't count the comments on one hand anymore unless you're that guy from The Princess Bride the bad guy who worked for the king.thnx for posting doe bug!
Jul 15, 2013

Jul 15, 2016

Jul 15, 2016

Good teaser. It's scientific and fun at the same time!

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