Microscope Lab

7/17/2019 Microscope Lab

1/10

The

Microscope

sffiffi

o

.

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Name

Partner

Date

Hour

The microscope,

eveloped

more

han hree

centuries

go,

s the

basic

ool of

the biologist.

A

microscope

enables

iologists

o investigate

iving

things and

objects

hat

are

oo small

o

be seen

with

the

unaided

eye.

The microscope

s

able

o

magnifr these

iny specimens

y

meansof

lenses

ocated

n the

eyepiece

nd objectives.

T[e [gtrt

microscope

s

also

capableof

revealing

ine detail.

This ability

to

reveal ine

aitiit

is known

as resolving

power.

The type

of

microscope hat

you

will

be using

hroughout

your

studyof

biology s the compoundight microscope.-

Specimens

hat

areviewed

under

he microscope

re

mountedon

one of

two types

of

glass

slides.

Prepared

lides

are slides

hat are

or

permanent

se.

ilet-mount

slidesare

or temporary

use.

Most

of the

slides

hat

you

will use

n biology

will be

wet mounts.

In

ybur

study

ofbiology, it

will

be

necessary

or

youto

estimate

he

engthand

width of

some

olfg,ur

specimens.

o measure

bjecti under

he microscope,

unit

called

he

micrometer

pm),

rygetimes

called

tfre

micton

(p),

is

used.

One

micrometer

quals

.001

millimeter;

one

millimeter

equals

1000micrometers.

Give

he

purpose

f

the

microscope:

Define

esolving

power:

Name

he

ype of

microscope

sed

n high school

biology

plasses:

Contrast

he use

of

prepared

and

wet-mountslides:

Name

he

preferred

unit

of measurement

or microscope

work:

Tell

how

many

micrometers

re

n

a

millimeter:

also

called

he

Give

the syrnbol

or the

micrometer:

Stage

opening

permits

ight

rom

ight

source

o

passuP hroughbody ub

Oiaphngm

regulates

mount

ol l.lght

passing

hrough

sPeclmen

Lamp

or

mirtor

directs

ighl

hrough

diaphragm

and

stage

openrng


2/10

Carrying the

Microscope:

Take

he microscope

rom

the

storagearca. Carry

he microscope

with

one hand

under

he base

and he

other hand

grasping

he

arm.

Place he

microscope

n the aboratory

able. The

microscope

hould

be

about

10

cm from the

edgeof the

table.

Uncoil

and

plW

the cord nto

an

outlet

at

your

ab

station.

The on(l)-otr(0)

switch

s

located

n

the

left

sideofthe base

ofthe

scope.

Parts

of

the Microscope:

Look at

he drawings

n

the

previous

age

hat

s

most ike

your

microscope.

Identifr

the

parts

and

unctions

of

your

microscope.

Cleaning

he Microscope:

Carefully

clean

he eyepiece

ndobjectives

enses

with lens

paper.

Locate

he

nosepiece

nd

gently

urn

it so hat the low-power

scanning

objective

s

in

line with the

body ube. The

nosepiece

ill

click into

place

when

he

objective s in

the

proper

position.

Field

of View:

Keeping

both eyes

opeo look

hrough

he eyepiece.

You will

seea

circle of light.

This s

called he

field

of

view.

To

make

he circle

of light

as bright

as

possible,you

may have

o adjust he

diaphragm.

Your

Dominant

Eye:

If

you

areobserving

hrough

a single

ens

monocular)

cope,

earn o

seewith

your

dominant

eye

while training

the other

eye

o

relax

and

not

concentrate

n anything. This

technique

s useful

and s easily earnedwith practice. It will come n handywhenyou drawyour specimens syou canuseyour

weaker

eye

o help

you

see

your

drawing

while

observingwith

the dominant

eye.

Right or

Left?

Which s

your

dominant ye?

In

order

o determine

hich

eye

s

dominant

stronger),

here s a

simple est.

Use

your

hands

o

form

a circle

at arm's

ength.

Look

acrosshe roonl

through he

circle,both

eyesopen

relax),

at some

object.

Slowly bring

he circle

oward

your

face. Your hand-

circle

will

probably

go

to oneeye

or the other-this is

your

dominant ye.

Use his

eye

or

viewing.

Describe our

hand-positionwhen

arrying

he microscope:

Give the

rulme

or

the

circle of light

you

seewlren ooking

through he

eyepiece:

Name

he microscope

art

used o

adjust

he amount

of light in

the field

of

view:

Contrast

a monocular

and binocular

scope:

Which

eye

s

your

dominant

eye?

There

are hree

objective enses

on

your

microscope.

The

shortest ens s

called he

scanning ens-it

has

a

red ring

around t. The ow-power

objective

s the

medium-length

ens

and has

a

yellow

ring

around t.

The

high-power

objective s

the

longest

ens

and has

a blue ring

around

t.

The

lens

you

are

using

s

the

one hat

is

clicked

into

place

above

he stage

opening. You

could also say

t

is

the

onebelow

he body

ube.

A4iust

your

micrqscope

o

he scanning

gns s

in

place

or viewine

a specimen.

People

normally

have

a

stronger

(dominant)

eye

the

one

hat is

mostused).

t is often

he one

used or

microscopic

bservation,

unless

you

are

using

a binocular

stereomicroscope.

Then,you

would

use

both eyes

o observe

your

object

or specimen.

z


3/10

Preparing and Observing

a \ilet

Mount

Obtain a

glass

slide

and cover slip. Wipe both sidesof

the slide with a

cloth to removedust,

etc. The cleaned

slide and cover slip shouldbe

handledby their edges.

Cut

out

a small

piece

of newspaperhat contains he

letter

e.

This shouldbe

a standard ewsprint

etter-

NOT a

headline-sizeetter-Avoid dark backgrounds

n either sideof the

newsprint.

Place he letter

e

in the

centerofthe

slide

as

t

would

appear

n

the

newspaper-face-up. ieht side

up.

Usinga

pipette,place

a

drop

of tap wateron top ofthe

e.

IJse

a

probe

o

hold he

e

in

place

while

you

add

the drop of water, f necessary.

Hold a coverslip at

abouta45o ang,le ver he dropof water.

Gently ower he cover

slip

onto he slide.

If

air

bubbles ppear,

ently

ap he coverslip

with

the

backend

of

the

probe.

Dissecting

eedle

Place he wet mount of the

letter

e

on the stageof the microscope

ryith he etter

facing

yor+

as

you

would

read t in

print.

Adjust

the slide

so that the

letter

s

above

he opening

of the stage.

Look at the slide

at

eye evel. Observe

he

space etween

he

slideand he scanning bjective.

The

scanning bjective

hould

be n line with the body ube

(over

the stage

opening).

Slowly

turn the coarse-adjustmentnob, raising he stage o its highest

position.

You

are

now ready o view

your

specimen.

Look through he eyepiece ndSLOWLY turn the coarse-

adjustment nobuntil

the

etter

e

comes nto

focus. Inthe

circle

below

(which

epresents

field

of view), sketch

what

you

see.

Calculatehe magnification

eyepiece

objective).

Show

your

math n the space elow.

Leave

your

slide on the stageandhave

your

instructorveriff

your

view. Your instructorwill

initial the blank below.

CAUTIONz

Never

raise the stage

while looking

through the eltepiece;

you may hit and danrage the slide or

ohjective ens. Look to the

side, raise

the stage to its nruxintum

height, then

focus

u,hile the stage

s movirtgAWAY

fi'om

the objective.

Completed

Magnification


4/10

Make

a second lide

of a etter

o'e

but

this time from

print

provided

by

your

nstructor.

Onceagain, heck he

orientation

f the etter

it

shouldbe n

the

same

osition

as t appearsn

print).

Rotate

he nosepiece

o

the actual ow-power

ens.

This s

the mid-length ens

with

a

yellow

circle)and s

markedwith

a magnification

f 10X.

Following

proper

echnique,

ocate

and ocus

on the etter.

Calculatehe magnification

elow

(show

your

math):

Sketchwhat

you

observe

elow.

Completed

Magnification

Paradoxical

Movement:

Themicroscope

xhibits

n optical

henomenon

alled

aradoxical

ovement.

Move

he slide

o the ight......Which

way

does t

appear o move n the ield

of view?

Move t

to the eft..

.Whichway

does t

o'appear

to move?

Move

he slideaway rom

you,

hen oward

you. Which waydoes t appear o moveeach ime? Whatdoes t mean

when

an optical nstrument

xhibits

paradoxical

movement?

Practice

entering

n object n

the ield

of view. For

example, n object s

on the edgeof the ield

of view

and

you

want

o center t

before

you

ask

your partner

o

takea look. Determine

which way

you

would

move

he

slide

o center he specimen.

Below

are

somesample

roblems.

Use

an arrow

or

two arrows)

o showwhich

way

you

would move

he slide

o center

he object:


5/10

To

observe

a specimen

at high-power

magnifrcation,

urn

the nosepieceuntil

the

high-power

objective

clicks

into

place. (The

high-power

objective s

the ongest

object,has

a blue

ring,

and s marked40X.)

You microscope

s

parfocal.

This

allows

you

to focus

he scopeat low

power,

switch o high

power,

and,with

only minor adjustment

of

the fine-adjustment

knob,

see he object

at

high

power.

For

that reason,here s

another

general

ule

of microscopy:

To view an object at high

switch

to high

power

and

Observe he etter

at

high

power.

Draw what

you

observe

Calculate he magnification

below

(show

your

math):

Completed

Magnification

Measuring

n

Object

Under heMicroscope

Turn

the

nosepiece

o he scanning ens

(4x,

40x

total) is in

place.

Place

a millimeter

scaleof a transparent

plastic

uler

over the center

of the stage

opening n

the microscope.

Use

he scanning

bjective o locate

he millimeter

ines of

the ruler. Place hese ines n

the middle

of the

field

of

view and

use he coarse-adjustment

nob

to bring

them n to focus. The

distance etween

wo lines on the

ruler represents

mm.

power, always begin by focusingon it at low power. Then,

use he fine-adjustment

knob

to bring the object into

view.

While looking

through

he eyepiece,

move

he

ruler

so hat

one of

the

millimeter lines

s

ust

touching

he

eft

sideof the

field of view.

You

ruler will look

like the

diagrambut

you

will be

able o see

more millimeter

lines since

you

are

working

at a lower

magnification.

To

determine

he diameter

of the field

of view for

the scanning ens,

count

he number

f millimeter

lines

(actually

spaces)

hat are

visible. You

will

need

o

estimate he

diameter

o the nearest

enth

of

a millimeter.

Field

of view

2 millimeters

Since

he micrometer

(pm)

is

the

preferred

unit of measurement

or

use with

the

microscope,

convert

your

measurement

n

millimeters

o micrometers

y moving

the

decimal hree

places

o the right

(effectively

multiplying

by 1 000).

Scanning ens

(4x,

40x

total) field

of

view:

mm

or


6/10

Next

rotate he nosepiece

o the ow-power

objective

10x,

100x

total) anddeterminehe ield of view.

Count

the number

of millimeter ines

hat are

visible. Since he

millimetermarks hemselves

re

now

rather arge,

you

will need

o move he edge

of oneof the

marks o the eft

sideof the ield of view and

count

rom

the eft edge

of onemark

o the eft edge

of the next. Don't

forget o estimate

he nearest .1 mm.

Low-power

bjective

10x,

100x

otal) ield

of view:

mm or

pm

Because

nderhigh

power 40x,

400x

otal) he

hickness f oneof the

millimeter

ines

akesup

practically

he

entire ield of view, t is difficult to estimatehe diameter f the ield veiwunderhighpowermagnification.

The

diameter nderhigh

power

can

be calculated n

paper,

owever.Here

are he steps:

l. Divide

the magnification

f

the

high-power

bjective

y the magnification f

the

ow

power

objective.

Show

your

math n the

space elow:

2. Then

divide the diameter

of the low-power

field size of view in micrometers

by the answer o the

step

one

above. Again, show

your

math:

High-power

bjective

40x,400

otal ield of

view: mm or

pm

Sample

problem:

Here s

what

you

see

n

your

scope

t

100x

using

he 10xobjective):

For owpower 10x, 00x otal):

of view

Edge

of ruler

Forhigh

power 40x,

400x otal):

Mill imeter

ines

(

2

mill imeters


7/10

Record

our

group's

ield

sizes or

the scanning

4x,

40x total), ow-power

10x,

00x

total),andcalculated

high-power

40x,

400x

otal) on

the data able n

class.The

class

will

adopt

a

standard

etof field sizes rom

class

data. Do not write

anything n

the section

elowuntil all the class

datahasbeen ecorded.

Class

tandards:

Prepare

a wet-mount

of a human hair.

Observeand draw

the

hair

at scanning, ow, and high

powers.

Low-power

x

High-power

To

calculate

he width of a human

hair, estimate

ow many

couldbe

placed

side-by-side

crosshe ield of

view. Divide

the sizeof the ield

of

view by this number.

Show

your

math or each

problem

n the space

below:

7


8/10

Practice

problems:

HumanHair

l00x

Human

Hair

400x

/t

Prepare

slide

of two crossed

hreads

f different

colors.

in the

space elow.

You drawings

hould

nclude

color.

View

the hreads t ow

power

anddrawwhat

you

see

Estimate

he width of the hreads.

CrossedThreads

Magnification

Width of a thread

pm

.

qrhPl [

o\

\ l iJ

U\

c,*1 ^\q{,

ons

:


9/10

Make

a

temporary

wet mount

of material

from

your'oPond

naJar

and

view

it using the microscope.

Attempt

to chooseone microorganism

and draw

it in the space

below.

Pond

n a Jar

Magnification

Width or

length

_

pm

\^ri

A+h

c.o.tc\^lslions

:

Continue

our

work with

the

pond

water

by

preparing

dditional

lide(s)and ocatingat east

wo other

microorganisms.

raw

hem n the

spaces elow

anduse he ield

guide

o

identi$z

hem.

Magnification

x

Width or length

Cq[o.rt\.^li

snr

..

Magnification

Width or length

C o.l.-,rl

{'on;

}

pm

pm

1


10/10

Label

the

parts

of the microscope

n the figure

below:

Looking

through he microscope,

n

what direction

does he etter

e appear o move when

you

moved

he slide

to

the

ieht?

to the eft?

away rom

you?

toward

vou?

What

is

the above

phenomenon

alled?

Calculate

he total magnification

of

your

microscope or

the following

objectives.

(Show your

math)

Scanning

Low-power

High-power

What

happens

o

the

focus

of the letter'oe

as

you

change rom low-power

to high-power magnification?

When

the aboveoccurs,

your

microscope

s

said o be

How many times is the magnification increased

when

you


to

high-power

masnification?

What happens

o

the size of

the

field

of

view when

you


magnification

to high-power

maenification?

How many

micrometers

are n a millimeter?

Give the

alternatename

for the

micrometer:

Give the unit for

the micrometer:

Give ts unit:

Microscope Lab

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