Zeeman Effect - Control light with magnetic fields-----make money online

today on Applied Science we're going to

talk about the Zeeman effect this is

another one of these cool

electromagnetic effects that reminds us

that electromagnetism basically controls

everything in the universe and it takes

a cool little demo like this to get a

visual representation of it so this kind

of similar to a video I did on the

Faraday effect recently so let's take a

look at the setup here we've got a low

pressure sodium lamp in the box here

with the diffuser just to give us a nice

orange light source and then we've got

an oxy-acetylene torch making a nice

stable flame here and then we've got an

electromagnet and this magnet has holes

going transverse through and vertically

through so that I can position this over

the flame like this so that the flame is

going up through the magnet but we can

still see the light through the holes in

the side there so let me move this out

of the way so we can see something else

for a sec you've probably seen the trick

where you dissolve some sodium nitrate

or even sodium chloride in water and

then just use a little bit of shoelace

or wick to introduce sodium into the

flame like this and this works just fine

but for today's demo I'm going to use a

little ceramic rod that's been heated up

very hot and then dipped in salt and the

reason that I do this is that the flame

that comes out is way more stable so

there's no spattering because there's no

water involved okay now with the magnet

in place the sodium in the flame if you

look down the barrel and turn the magnet

on and off this is what you see pretty

cool right the first thing that's weird

is that the flame is actually

obstructing the light that's coming out

from the sodium lamp and then you can

see when I turn the magnet on and off

the flame becomes opaque or less opaque

depending whether the field is on or not

you know similar set up we can use the

little projection lens here to make an

image of the flame that's inside the

magnet and projected onto the paper

there and so same deal if you look at

the image of the flame on the paper and

then I turn the magnet on and off you

can see the flame is suddenly dark and

bright what's happening is it's

obscuring the light from the lamp or not

obscuring it as much hence getting

lighter and darker it's so cool I really

love these effects where you can

use magnetism to control light directly

like there's no device in here it's

literally just the atoms responding

directly to the magnetic field so let's

parse what's going on in here if we've

got this low pressure sodium light

giving off light you can see that when

the flame is neutral or doesn't have any

ions in it especially it's clear so we

can see the light from the sodium lamp

no problem but if we introduce sodium

ions into the flame something weird

happens the flame actually blocks the

light from the sodium lamp and if you

think about it and sort of a hand-wavy

sense this kind of makes sense it's sort

of like we've got sodium ions giving off

light in the light source then if we put

more sodium ions in front of it it's

kind of the same thing and so it's

blocking the same wavelength of light

you can see that there's a balance here

too so the hot part of the flame is

giving off more light than is coming

from the lamp behind it but up near the

top of the flame there's sort of just

the right balance of sodium ions to

absorb the light and make it look darker

than the light source that's coming from

behind it so to do this experiment you

sort of have to fine-tune where we are

in the flame so that we get this kind of

opaque effect another interesting way to

see this is to start with a white light

source and I'll put a slit in front of

it and then look at that white light

source with a diffraction grating so

that we can see the whole rainbow then

if we introduce sodium ions into the

flame of an alcohol lamp you can

actually see that the sodium ions absorb

that orange light and it's a very narrow

specific band if we zoom in here you can

see just a little sliver of the spectrum

missing when I introduce the sodium ions

so they're clearly absorbing that one

color now the Zeeman effect says that we

can shift the exact point that the

sodium ions absorb or emit light by

putting it into a really strong magnetic

field and so the trick here is that if

we have this flame or packing effect

going on where we can't see the light

from the light source through the flame

because they're at exactly the same

spectral range they're right on top of

each other in terms of spectral lines

but if we put the flame in a magnetic

field then it's exact line won't line up

with the line from the light source

because this magnetic field is

actually shifted the lines position a

little bit and that's exactly what's

happening here so we we turn on the

magnetic field the flames orange becomes

a very slightly different shade of

orange than the light coming from the

light source behind it and this opaque

effect goes away because the lines don't

line up anymore

I originally saw this demo from another

YouTube channel called EXO funk oh X and

you should definitely go check out their

channel they've got a lot of really cool

physics demos I thought this was really

creative because normally to see the

Zeeman effect all they do is sort of

turn on the magnetic field and through

looking through a spectroscope you can

see the line divided into two lines

because of this magnetic field and

that's cool and everything but I really

like this flame of baking effect because

it it's a very elegant way to show it in

a very you know kind of hands-on way so

here's the hand wavy explanation for why

this effect occurs think about what

gives sodium its characteristic color

when you excite the atoms either with

high voltage or a flame they move up

into a higher energy state and then when

they fall back down to the ground state

they emit this characteristic color and

so for sodium ions it's this orange

color dominated by the two spectral

lines there and for something like neon

it's a red color okay cool

in a really strong magnetic field it

will alter the the state this elevated

state that the atom can go into and the

reason is that electron shells are

basically moving charge and moving

charge is basically a magnetic field so

if you put the atom into a strong

magnetic field and excited it will

actually go up to an either higher or a

lower energy state depending whether it

agrees with the polarity of the field or

not

so the Zeeman effect basically splits

one spectral line into two or more and

the reason it can be even more is

because there's multiple electron shells

in the atom and the Zeeman effect will

affect all of them in different ways it

gets pretty complicated and if you go to

the Wikipedia page it's really heavy on

the physics and the equations and it

doesn't really help give a qualitative

sense or understanding of what this is

this effect actually crops up in lots of

different places though for example MRI

machines rely on this for their basic

function so when you go into an MRI

machine you're going into a really high

magnetic field and all the atoms in your

body and now have these additional

energy states and so when the machine

excites them the whole reason the system

works is because it gives them these

different places to go through the

Zeeman effect another really cool

application of this is for astronomers

so if you look at the light from a star

or even our own star the Sun if there's

a strong magnetic field there we can

tell that it's exactly what the

magnitude of the field is based on how

far the lines have shifted due to the

Zeeman effect so we can do experiments

on the ground and we know that you know

for example helium emits at exactly it

was a certain frequency but we know that

if helium is in a certain magnetic field

if the lines will actually be split and

then if we measure this split we can

tell the magnetic field and that's how

we know that sunspots actually have

really strong magnetic fields let's take

a look at some of the practical details

for doing this experiment the light is

an 18 watt low pressure sodium lamp that

I got off Amazon you can shift next day

I love this the only problem is finding

a ballast for it is not so easy

so people have come up with sort of

clewd solutions and here's one of them

I basically cracked open the base of a

cheap compact fluorescent lamp and took

out the circuit board and it's here and

the trick is that a compact fluorescent

lamp has filaments in either side so

it's like a four terminal device but the

low pressure sodium lamp only has two

terminals so I just put resistors on the

circuit board to mimic the resistance of

these filaments and that caused it to

start working and it's it's running just

about properly it's an 18 watt light in

my setup it's only drawing about 13 or

14 watts and so it's slightly under

driven but the warm-up sequence is

pretty cool these low pressure sodium

lamps contain a mix of neon and argon

and that's actually the color that you

see when you first turn them on and then

over the course of you know 10 minutes

or so the sodium vaporizes and starts

giving off the majority of the light the

electromagnet is made from two microwave

oven transformers that I cut open

and then removed the high-voltage coil

and also cut the middle pole piece to

try to get some flux concentration we

want the field to be really strong and

concentrated into a small area so it

works out to cut the pole pieces like

this and then I added a little bit of

extra material here so we had a gap so

that we could look through the magnet

horizontally and vertically the magnetic

field has to be pretty strong to see

this effect we're talking about 1 Tesla

of magnetic field and so this is not the

first electromagnet that I built the

first one I thought looked really great

but I tried making it work for days that

actually never got the effect out of it

and so I resorted to buying this

magnetic field meter and this is

actually proven quite handy so here's

the startup sequence my power supply is

actually a welding power supply that I

added some instrumentation to and it

won't start up when it's when it has

this much of a load on it so I turn it

on first with the throttle down all the

way and then connect it up and it's

drawing about oh I don't know five amps

or something idling and I'm going to put

the magnetic field gauge into the gap

and we're getting about half a Tesla

pretty good so I'm going to crank it up

and at maximum power it's doing about 1

Tesla or 1.1 1.2 Tesla and this thing

can only run in at full power for bursts

of you know 10 or 20 seconds I if I'll

turn this off first if I put my hand on

here it's it's already warm and the

other downside is this thing is kind of

in the flame and so everything is

heating it up but it's not really a

long-term experiments of course

initially I also tried doing this

experiment with permanent magnets and so

I have these really thick like half-inch

thick neodymium magnets and after I got

the flux meter here I measured them and

is very surprised actually quite

impressed that it's doing about point

eight of a Tesla and this should be

enough to see the effect the only

problem is that you mechanically have to

move the magnets in and out of the flame

path and just the fact that you're

putting this cold metal next to the

flame changes how the ions are emitting

light so you can kind of convince

yourself the effect is there but really

if you just take cold pieces of metal

spaced about like this and you move them

in and out of the flame you can kind of

see it changing the characteristic and

so it's it's too tough to really see the

effect

I also learned quite a lot about

engineering electromagnets I even did

some equations and stuff to figure out

what was going to work the best how to

optimize the most magnetic field for

kind of the least amount of copper and

the least amount of energy and I've been

wanting to do a video on magnetics for a

long time like how to choose toroid

material and what's the difference

between ferrite and iron powder and the

electrical steel versus iron and all

these things and so that's going to be

the topic of next video and I will see

you then see you next time bye

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