Control light with magnets and olive oil?! (Faraday effect)----make money online

take a look at this I've got a light

source here and then I've got a

polarizer in front of it and then over

here I've got another polarizer and

these are oriented 90 degrees to each

other they're crossed meaning that very

little light gets through the pair but

because they're imperfect even at 90

degrees a small amount of light will

leak through if it's very bright okay to

this I'm going to add a beaker of olive

oil and then I'm going to put into the

beaker a coil of copper wires the few

thousand turns of copper wire and going

to lower this down in here so that we

can look down the bore okay so now I'm

going to move the camera down to bench

top level so that we're looking through

the polarizer through the coil and then

through the other polarizer and I'm

going to control the power through the

coil with this switch crazy right did

you expect that to happen I actually had

no idea the effect would be so large so

at first you might be thinking oh it's

probably a problem with the experimental

setup like maybe the coil is pulling

something near it and it's you know

causing the light to be darker no that's

definitely not it and then you might be

thinking well maybe it's a liquid

crystal effect like you know the heavy

oil molecules are you know changing the

polarization of light or something no

that's actually not it either it works

just fine with plain old distilled water

if the effect is not quite as strong as

in the olive oil but it's still there

and water is definitely not a liquid

crystal this phenomenon called the

Faraday effect actually occurs in almost

all transparent materials and what's

happening here is when there's a

magnetic field in the direction that the

light is traveling through a substance

it rotates the polarization of the light

very slightly so if we're sending in

vertically polarized light if we have a

strong enough magnetic field over a big

enough distance in in the material then

we can actually rotate that field

slightly so if the two polarisers star

90 degrees relative to each other you

know it's very dark almost no light is

getting through but with a small amount

of rotation added in between them we get

a little bit more light through it the

effect happens in air too it's just that

air is so much less dense than the olive

oil or the water you can't really see it

so here's the setup with just air as you

can see there's there's no visual

effect also plain glass is not very good

at this either so here's a borosilicate

capillary that I have and I didn't

polish the ends but I don't think that

matters too much as you can see the

effect is pretty slight but not nearly

as big as the water or the olive oil on

the other hand if we add something to

the glass this is a I believe a

neodymium glass laser rod you can see

the effect is strong again and just to

really show that this is a magnetic

effect here's a permanent magnet being

lowered into just plain distilled water

and as you can see when I get the magnet

close the amount of light changes even

more interestingly when I rotate the

magnet from side to side when the

magnetic field is in the direction of

the light travel you can see that the

light is affected differently when when

the magnet is rotated and is transverse

to the light Direction pretty cool it

even works with just a vial of water so

if I get the magnet close to the side of

the vial and then pull it away and put

it back you can see the light levels

changing so what's actually going on

here well the hand wavy explanation is

that all matter is made up of atoms

which have electrons in them and

electrons being charged particles are

affected by magnetic fields so that when

an incoming photon interacts with those

electrons in the matter if it's in a

very strong magnetic field everything is

going to be affected and there you go

unfortunately the complete description

is fairly difficult and beyond the scope

of this video but I will put links in

the description for those interested if

you're interested in playing with this

yourself I have a few tips for you first

when I was looking for this effect I

used a really strong neodymium magnet

and a vial of olive oil and I tried

every combination of you know putting

this thing around and staring through it

in the dark and I couldn't get it to

work so originally I thought that the

effect was just too small to see with

the naked eye and if you look around on

the net you know most of the

documentation is using photo multipliers

or photo diodes and I thought others you

know there's just no way you're going to

see this with the eye however the

problem is with the magnet with a single

magnet like this you'll almost never get

this to work and here's why so this

magnet is north and south on the flat on

the large flat faces and the field

around

the outside looks sort of something like

this so there's actually a very small

region where the field lines are

parallel and strong so that the strength

of this magnet is mostly high out near

the poles here and it's weak over here

and if you put this near a vial hoping

to see the effect

you'll only get this faraday effect when

the light is traveling in the same

direction as the magnetic field lines

which means only this little slice right

here and since the effect is so we

really need these lines to be extended

over a large area to view it so what I

did

okay we're back and my fingers are okay

what I was going to say was that this

magnet is configured a little

differently so that the field has to

come out from one side and then it

travels through a longer distance here

and because there's north south and then

south north south again that the shape

of the magnetic field out here is much

more parallel for a longer period or for

a longer space there's a really cool

practical application of the Faraday

effect let's say we have one polarizer

like this and then another polarizer

that is 45 degrees not 90 degrees

twisted and then we set up our coil with

the special high Faraday or high verdict

constant material in there and the

rotation is 45 degrees so what will

happen is the light will go through the

first polarizer so now it's just

vertical polarized and when it goes

through our Faraday rotator what's now

plus 45 degrees and when it hits this

polarizer which is at 45 degrees you

know all of it goes through so the whole

system is as efficient as it can be

however if you try to send light in this

way it hits this polarizer which is plus

45 and when it goes through the Faraday

rotator instead of being reversed back

to vertical the magnetic field is now

going the other direction so instead it

spins the light another 45 degrees and

now it's 90 and then when it hits this

polarizer none of it goes there were

very little goes through pretty weird

right there's not too many substances

that do this in fact you've probably

never encountered one or if you look

through it it's clear in one direction

and you look through it and it's opaque

in the other direction

and in theory you wouldn't really need

our source you could do this with

permanent magnets even the problem is

getting 45 degrees of rotation is quite

difficult as you saw with our experiment

doing you know an amp and a half with a

few thousand turns is just enough to get

like a couple degrees of rotation so

getting all the way to 45 degrees of

rotation is not easy the materials

ability to perform this phenomenon is

called the verdict constant and it has

units like radians per Tesla meter so if

the magnetic field is longer then it's

you know bigger and if the magnetic

field is stronger then we get more

effect or the material itself can just

simply have a higher constant I haven't

found a good list of verdict constants

for various materials but keep in mind

that gases are almost certainly going to

be less than liquids and solids it's

also easier to see this with an

electromagnet anyway because you can

turn the magnet on and off without

disturbing the set up so it's easier to

see the brightness change and in this

case I'm using a solenoid

I just liberated the coil from this

mechanical solenoid and I believe it's

about 60 ohms as near as I can tell

maybe a few thousand turns of wire and

we're drawing you know about an amp and

a half almost at 60 volts for this thing

so it's quite a bit of power you can't

really leave it on but luckily if it's

submerged in water or oil anyway you

won't have any heat buildup problems the

last thing to consider is the quality of

these polarisers it might work with low

quality polarisers that you can get from

sort of cheap you know kind of home

science kits I actually got these from a

polarizer manufacturer and this was the

most restrictive polarizer they make so

not necessarily expensive but just very

restrictive meaning that they don't

transmit a whole lot of light as you can

see there they're dark they're less than

50 percent transmissive but they do

restrict they have a very high

extinction ratio as it's called meaning

that when they're crossed it's very dark

finally you'll have to use glass to

contain the substance you want to

inspect so you'll probably laugh at me

for doing this but I made this really

cool little plastic olive oil container

this actually fits down into the

solenoid coil really well and then I

found out oh yeah I use plastic end caps

on this and guess what the plastic

randomizes the light polarization all by

itself so you can't use a plastic

container

because it's going to ruin the

polarization and the whole thing just

won't work but wait there's more you

might be thinking well if a magnetic

field affects a transparent substance

what about reflections and yeah it's

true actually so if you have you know

reflective substance in a magnetic field

and you shine polarized light on it will

it be affected based on the polarization

or will it be affected by the

magnetization of the surface yeah it's

it's called the correct and I'll do a

future video on that but I haven't been

able to see the effect myself yet

because it's even weaker than the

Faraday effect but it will be coming up

in a future video also if you want one

of these iron-on transfers that you can

attach to your lab coat or clothing let

me know if you're already a contributor

at patreon just send in your address

make sure you sign up for this reward

before the end of the month and I'll

mail this out - I also have extras so

we'll probably be doing another giveaway

at some time in the future ok see you

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