Brain Teaser #72

Greg Bernhardt

Enter through one, exit through two, then enter through two, exit through one.
What is being enter/exited?

BoulderHead

Airport security checkpoints? [:D] [6)]

himanshu121

[o)]

1 and 2

2 and 1

hemmul

A lumped element in a alternative current circuit :)
1 and 2 are its "starts" and "ends", which are equivalent in an alternative current circuit...

Achy47

Your hands. Putting on and then taking off a T shirt.
Oops,,, I meant to say the shirt was he thingy bieng entered then exited.

Probably a beter thing would by the same relation on your pants considering feet?
But let's not go there, these mofos stink![g)]

MathematicalPhysicist

my answer is air. air enter in our mouth (which is one) and can exit through our nose (which has two holes [sorry for the bad terminology] and opposite as well.

meteor

Water in a conduct with form of Y?

Njorl

A Mach-Zender interferometer. I don't know if it is the answer you're looking for, but it fits perfectly.

Njorl

hemmul

What about elevator? Enter "though" first floor, exit through "second", then vice-versa and go home... eh? [;)]
also could be a train: enter at station A through the left door, exit at station B through right door, then from B to A in a different manner...

however, a capacitor in AC circuit fits more...

Achy47

Any one of the 4 areas created by two non-paralell infinite lines in R^2. You can cross through either at the intersection - (through 2), or not: (through 1).

MathematicalPhysicist

what is A Mach-Zender interferometer?

Njorl

In a Mach-Zehnder (I spelled it wrong initially) interferometer, a single beam of light enters, is split into two beams which travel identical pathlengths through an electro-optically active material, such as lithium niobate or gallium arsenide, then recombined. While the beams are seperate, one of them is subject to a slight perturbation. This usually takes the form of an applied electric field. The index of refraction that one beam experiences is slightly alterred, making it experience a slightly different path length. With the correct bias, you can induce a pi/2 phase shift in one arm of the interferrometer. This allows you to modulate the throughput signal from 0-100% at very high speeds (>100 GHz).

Edit - Just wanted to add, I worked on a rib-waveguide version of this. When I read the riddle, I thought of it immediately. We made it by combining elements we already designed - a 1 to 2 splitter and a 2 to 1 combiner - one entrance two exits, two entrances one exit.

Njorl

MathematicalPhysicist

dare i to argue that the first beam of light is different from the end product when the two seperated beam combined?

Njorl

In the "on" state, the beam would ideally be unalterred. Besides, when a child walks into school in the morning and leaves in the afternoon, is it the same child?

I'm sure there is a better answer. I just can't think of it because I have my MZI on the brain.

Njorl

MathematicalPhysicist

but you said: " While the beams are seperate, one of them is subject to a slight perturbation."- therfore i assume the beam is seperated to two beams which is encouters to something that changes something in it therfore when they combine they are different from each other.

gnome

A heart?

Enter through one right atrium, exit through two pulmonary arteries, enter through two pulmonary veins, exit through one aorta?

(It would work better if I could say, enter through one vena cava, but there are 2 of those.)

Bailey

don't think is the blood in the heart, since blood from the right atrium, exit throught 1 pulmonary trunk, then enter 2 pulmonary arteries.

i was thinking about excretory system too, but too lazy.... the question is kinda ambiguous.