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How To Use a Compound Light Microscope: Biology Lab Tutorial

this video is an introduction to the

parts and operation of a compound light

microscope

once you transport your scope back to

your station

remove the dust cover fold it up and

place it in and out of the way location

to keep your workspace uncluttered

whenever you transport your microscope

you want to make sure to hold it both by

the neck and the base this scope has a

nice handle right in the nut and then

have your other hand and needs banks

depending on the type of scope you have

you might need to plug a loose cord into

both the scope and the outlet or if you

have a scope similar to this the cord is

attached to the microscope and you just

need to unwind the cord and plug it into

an outlet compound light microscopes

typically have an on/off switch in the

base this switch lights up when I have

it turned on

understanding how to adjust the amount

of light that shining through your

specimen is an extremely important skill

to have too much light and your specimen

can be washed out too little light and

there's not enough illumination to see

it adjusting the light allows you to

manipulate contrast that's the

difference in the visibility of your

specimen versus the background most

compound light microscopes have a dial

that will adjust the light level from

the illuminator in the base another way

that your scope allows you to adjust the

amount of light shining up through the

specimen is through manipulation of the

iris diaphragm

this mechanism is located directly

beneath the stage and you twist it to

open and close the iris

you

a mechanical stage is a very handy

feature to have on your scope you can

place your slide into the slide holder

and then adjust the position of your

slide using the coaxial adjustment knobs

usually hanging off the side of the

stage

this way you can Center your specimen

very easily

you

the focus knobs raise and lower your

stage and the vertical position of your

specimen is what determines whether it's

in focus or now

on this scope the course focus can be

adjusted by turning the part of the knob

that's closest to the body of the scope

the fine focus can be adjusted by

manipulating the outer portion of this

knob doing so fine-tunes the image of my

specimen

compound microscopes have either a

single ocular lens or a set of binocular

lenses the ocular magnifies the specimen

ten times actual size

the objective lenses are located on a

rotating nose piece each lens hangs down

from this nose piece and can be turned

and clicked into position the shortest

objective lens is called the scanning

power it has a red band around it and it

magnifies the specimen four times actual

size however since I'm always looking

through both the ocular and the

objective to view my specimen I multiply

the powers together to get my total

magnification

so the ocular magnifies ten times the

scanning magnifies four times meaning at

scanning power my total magnification is

40 times actual size the next objective

lens is the low-power lens it has a

yellow band around it and it magnifies

objects 10 times actual size so the

total magnification when using my

low-power lens is the ocular which is 10

times x the low-power lens which is 10

times magnification as well for a total

magnification of 100 times actual size

now when I switch to the next objective

it looks kind of funny the lens is

covered up with a finger cut in the lab

where I teach these scopes are primarily

used for microbiology classes in in

micro we're mainly using the oil

immersion lens the black and white

banded lens for viewing at high power

and the oil use with this lens can

damage our hydride power lens that's why

we cover it up but for now we need to

uncover the lens and take a look at it I

can dispose of that finger cut and now I

can see my high dry powered lens this

lens magnifies specimens 40 times actual

size but again I'm always looking

through the ocular and the objective at

the same time so my total magnification

at hydropower is 400 X 10

compound microscopes typically have

three or four objective lenses if you do

have a fourth lens that would be the oil

immersion lens it has a black and white

band around it it magnifies objects 100

times actual size so together with that

ocular lens of ten times magnification I

can get a total magnification with oil

immersion of 1000 an important warning

whenever you are using your high dry

objective or your oil immersion

objective these are your two longest

lenses never ever ever ever ever ever

ever adjust the coarse focus when you're

using these longer lenses you're only

allowed to use the fine focus again that

knob that's set within the coarse focus

knob manipulating the coarse focus when

using these longer objective lenses will

at the very least take your specimen out

of focus immediately and worst-case

scenario could smash the lens into the

slide damaging the microscope when

you're all done it's important to put

away your scope properly so that it

won't get damaged you do this by making

sure that the shortest objective lens is

pointing down the scanning power then

you dial the coarse focus stone all the

way to lower the stage as far as it can

go this way

we know that the lens is not going to

smash into the stage more seriously

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