LEEF Training event: Using microscopes with children and young people
USING MICROSCOPES WITH CHILDREN AND YOUNG PEOPLE
Wednesday 23 November 2015, 9.30am-3.45pm
South London Botanical Institute SE24 9AQ
Programme:
9.30-10 Arrive and coffee
10-10.15 Introduction to the day
10.15-11 SLBI Garden in Focus — hands-on session exploring opportunities for microscope work in
the KS1/2 science curriculum
11-11.15 Tea/coffee break
11.15-12.15 ‘Interpreting the image: Arts/Science Projects using microscopes at Roots and Shoots’
-Dr David Perkins, Environmental and Educational Resources Manager at Roots and Shoots. David
will examine what we can learn from watching live micro-organisms (e.g. in pond water) about life
on earth - ecology, evolution, relationships.
12.15-1.15 Lunch and an opportunity for a private viewing of the art exhibition ‘The Fox Got you’, a
photographic installation celebrating six common plants which are the origin of five major
medicinal drugs.
1.15-2.15 The wonderful world of microscopes: using them in environmental education with
children and adults— Dr June Chatfield, well-known naturalist, Vice President of the British
Naturalist Association, Fellow of SLBI and former lecturer in Environmental Science. June has
promised some technical detail about magnification levels and light sources plus a look at mosses
and lichens and some refrigerated leaf litter invertebrates.
2.15-3.15 ‘Stepping Inside the cell-Microscopy for Primary School Children’ — Dr Claire Wells,
Senior Lecturer in the Dept of Cancer Cell Biology and Imaging at Kings College London and Royal
Microscopical Society committee member. Claire will be talking about an outreach project she ran
for KS2 children and we will all get a chance to familiarise ourselves with the processes of making
slides and images under her expert tuition.
3.15-3.45 Tea, cake and feedback
LEEF Training event: Using microscopes with children and young people
Microscopes: Some definitions of terms
Optical microscope—a microscope that uses visible light to make an image. The light is refracted with
optical lenses to create the image.
Compound microscope—a microscope with two lens systems: the objective and the eyepiece or ocular
lens. Both eyepiece and objective lens may be replaced or rotated to give a range of possible
magnifications and resolutions. Compound microscopes may be monocular or binocular but both eyes
share the same view producing a 2D image.
Stereo microscope—a microscope with two eyepieces whereby each eye sees a slightly different image to
create a stereo or 3D view (relies on the principle of Victorian stereoscopes to create a 3D picture). Stereo
microscopes are always binocular.
Binocular—a microscope with two viewing tubes. May be more comfortable if using all day every day.
Adjustable but be aware that may not be sufficiently adjustable to fit very small faces of young children.
Monocular— a microscope with a single viewing tube.
Objective—the lens at the end of the microscope view immediately above the specimen.
Ocular lens (eyepiece)—the lens that the viewer looks through.
Total magnification—the sum of eyepiece x objective magnification, see also resolution below.
Resolution—this terms refers to the amount of detail that will be captured and relayed to the eyepiece i.e.
the ability to show fine detail in the image. The resolution of a microscope image depends on the objective
lens: the eyepiece lens can magnify that image and make it bigger but not more detailed. Thus a
microscope with 40x magnification on the objective lens and 10x on the eyepiece will create a higher
resolution (sharper detail) image than a model with 20x magnification on the objective and 20x on the
eyepiece lenses although total magnification will be x400 in both cases.
Field of view or depth of field—the diameter of the circle of light that you see when looking into a
microscope. As the power gets greater, the field of view gets smaller i.e. field of view is less at higher
magnifications. There is less need to move the slide/specimen about when working with a wider field of
view (because you can see more of it).
Coarse focus—the rough focus knob which adjusts the distance from the objective to the specimen and so
moves the subject quickly through the focal plane. Many less complex microscopes only have a coarse
focus function.
Fine focus— the knob used to fine tune the focus on the specimen, normally one uses the coarse focus
first to get close then moves to the fine focus knob for fine tuning.
LEEF Training event: Using microscopes with children and young people
Achromatic lens—a lens which has been corrected so all chromatic (colour) and spherical (focus or flatness
of field) aberrations are restricted to the outer edges of the field of view (normally the outer 40%, higher
quality lenses that restrict aberrations to the outer 20% or are even 100% corrected are available but are
very much more expensive).
DIN standards—Deutsche Industrie Norm i.e. German standard for the manufacturing of microscope
lenses which has been adopted internationally (and replaced earlier standards such as the RMS
standard). DIN lenses aren't necessarily better than non-DIN but they will be interchangeable from one
DIN microscope to another. JIS is the Japanese equivalent standard. Note that there is no equivalence
between these three standards.
Questions to consider when purchasing a microscope
What will you use it for most frequently? (3D opaque objects or 2D transparent ones?)
Who will us it most frequently and what level of expertise will they have? (What age? If you envisage using
microscopes mainly to cover cell biology components of KS3/4 science curriculum you might choose very
different model to someone working mainly looking at pond and leaf litter invertebrates with primary
school age children.)
Where will they use it? (In the field? In a multi-purpose space? At a dedicated microscope station? Does it
need to be cordless? Implications for light source.)
How robust should it be? (Age of users, portability etc)
What magnification is appropriate? (How deep into the cell do you want to go?) And at what resolution?
How precise/fiddley do you want the focusing to be?
How tricky do you want sample preparation to be? (slides, sections, staining etc)
How long will people be using the microscope for in any one session? (Comfort of user: angled eyepiece/s
rather than straight above and binocular? But also light source may need to be a ‘cool’ light source e.g. LED
to avoid frying specimens.)
What’s your budget?/Are there any grants available?
Do you want to be able to purchase additional eyepieces/objectives to increase the range of use to which
you can put the microscope? (If so, you will need a microscope which is modular construction and meets
DIN standards.)
Do you want to attach a camera/video camera/be able to show the images on computer screen?
LEEF Training event: Using microscopes with children and young people
Specific considerations when using microscopes with children
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Monocular or binocular: mono might be advantageous for the very young who may not be able to
adjust two eyepieces close enough together for satisfactory use.
Robustness and stability may be of increased importance: less stable microscopes are more prone
to picking up vibrations and transferring these to the image which can make it fuzzy and less
satisfying.
Relationship of the image to the specimen (children esp. younger children e.g. KS1/2 will find it
easier to relate to a crisp clear, upright image which can be related to the item they are viewing
without too much interpretation. Counter-intuitively, lower magnification e.g. 10x or 20x may be
better because it facilitates this connection: seeing a detailed image while being able to handle the
specimen can be a very convincing learning tool).
How simple do the controls need to be (one knob to focus and single objective with limited risk of
sending objective crashing down into the sample; ability to control lightsource—thankfully old style
fiddley microscopes that some of us might be old enough to recognise from our childhood with a
rotatable mirror under the viewing stage have been supplanted by electric lighting with most
student models using LEDs, but some still rely on a natural light source; field of view—how much of
the specimen do they need to be able to view without needing to move it once all set up and in
focus? Etc) Note that models with a fine focus function may be trickier to focus but can provide a
clearer image which is more relatable for younger children.
Will children be sufficiently old/experienced to prepare slides (scalpels, glass slides, chemical stain)
or will it be more useful to have a microscope able to view 3D objects such as dead bugs or
seedheads which can be popped under as they are or mounted simply on card?
Is a microscope the most appropriate way of magnifying something for very young children? Simple
magnifying glasses or cheap handlenses may achieve the desired goal more simply.
LEEF Training event: Using microscopes with children and young people
Comparative features of different kinds of entry-level microscopes
Some considerations apply regardless of the type of microscope selected. For example, metal microscopes are more durable and provide greater stability than
plastic; better quality optics provide better quality images (glass not plastic)
Type of microscope
‘Toy’ microscopes
available from
department stores and
educational toy stores
Main features
Often claim high linear
magnification e.g. 500x
or even 1000x.
Brightly coloured plastic
body with plastic lenses.
Introductory monocular
microscopes e.g. Motic
MS2
Relatively low
magnification.
Monocular.
Upright image.
Large simple controls.
Removable base plate.
No sample preparation
necessary.
Advantages
Light and portable;
bright colours attract
very young children.
Disadvantages
Insufficient resolution to
view images at the
stated magnification
(need careful sample
prep, good optics and
specialised lighting to
get good results at such
high magnification):
produce poor quality
fuzzy images.
Not very stable:
vibrations make poor
quality image even
more blurry.
Poor quality plastic
lenses are not corrected
for lens errors.
Generally metal and
Coarse focusing only.
better quality than toy
Monocular may not be
microscopes mentioned comfortable for
above.
prolonged viewing
Easy to relate image to
(although binocular may
specimen viewed. Single not be suitable for
magnification (usually
younger children in any
20x) enough to see
case).
Guideline price
£25-50ish
Child-friendliness
Poor: frustrations
involved in using these
toys can put children off
rather than encouraging
them into the
wonderful world of
microscopy.
£60ish (and RMS grant
may be available)
A good general
introduction to
microscopes for
children and adult
beginners.
LEEF Training event: Using microscopes with children and young people
Stereo microscopes
Binocular with each
eyepiece giving slightly
different view to create
3D image.
Upright image.
Low magnification (5x40x)
Good depth of field.
More complex models
have interchangeable
objectives with different
magnifications.
Focusing knob plus
height adjustment on
stand for larger or
smaller objects.
Built in lighting at top
and base (depending on
model).
detail not apparent to
naked eye but not so
much as to make it
unrecognisable.
Single eyepiece may be
easier for young
children.
No sample preparation
required: pop it under
and go.
Wide field 3D image the
right way up is easy to
relate to the specimen
under view.
Good for opaque 3D
subjects.
No sample prep
required.
Single magnification
only (usually 20x).
Tend to rely on natural
light which can be tricky
in some contexts.
Binocular eyepieces
may be insufficiently
adjustable for young
children.
More complex to use
especially if
interchangeable
objectives.
Height adjustment risks
objective lens toppling
on to specimen to
detriment of both.
£75 upwards depending
on versatility of the
model selected.
Easy to relate image to
object and able to look
at whole range of
common 3D objects
without needing to
prepare the specimen
or fiddle with artificial
light sources. Low
magnification means
less abstraction from
the real world.
Binocular may be
confusing.
More versatile models
are significantly more
complex to use.
LEEF Training event: Using microscopes with children and young people
Compound microscopes
Light is shone through
subject so prepared thin
specimens are needed.
Higher magnifications
are possible (e.g. 50x400x)
Image is inverted.
Shallow depth of field.
Binocular or monocular
(but each eye sees same
image).
Modular construction
means range of
eyepieces and
objectives can be used
to give range of
magnifications and
resolutions.
Fine and coarse focusing
Able to see cellular
structure of plant and
animal specimens.
Wide variety of preprepared slides are
available.
Sample preparation is
£60-180ish
required.
Harder to relate higher
magnification inverted
image to the object
under view: may require
interpretation.
Complex focusing.
External lighting is
required.
Inverted image makes
orientation confusing.
Complex to use
requiring more time for
instruction.
Lower depth of field
makes it trickier to ‘find’
the specimen.
The only type of
microscopes capable of
looking at e.g. the nuclei
of cells or bacteria.
LEEF Training event: Using microscopes with children and young people
Recording images
Microscope images, moving as well as still, can be recorded very simply using a compact digital camera, a
webcam or even a mobile phone. These devices can be regarded as ‘electronic eyeballs’, and so are
capable of picking up an image when placed at the eyepiece of a microscope. A couple of simple conditions
apply. First, the height of the camera lens above the eyepiece must be arranged so that the full field of
view of the eyepiece can be seen. Look for the ‘exit pupil’ of the microscope – the small patch of light that
comes to a focus 10–15 mm above the top of the eyepiece and which can be seen by holding a piece of
thin paper above the eyepiece. The exit pupil normally falls on the pupil of the eye, and similarly needs to
enter the camera lens if the whole field of the eyepiece is to be seen. Some cameras with large and
complex lens systems and some eyepieces with a low exit pupil will not be suitable; in general, the smaller
and simpler the camera the better. Ideally, some system of supporting the camera in the correct position
should be devised. At its simplest, this could take the form of a piece of thick wood with a hole to
accommodate the eyepiece tube, forming a platform for the camera to rest on. The hole can be lined with
strips of the soft half of self-adhesive Velcro to provide a friction fit. Second, since our eyes are generally
focused on infinity when looking through a microscope, where possible the camera autofocus should be
disabled and focus set on infinity. The flash, if any, should be disabled.
With thanks to Peter Evennett for the information in this section which is taken from his article:
Smaller than we normally see: the fascination of microscopy is not restricted to biology SSR March 2011,
92(340).
Further detailed advice on attaching a camera to a microscope can be found at:
http://www.microbehunter.com/connecting-a-camera-to-a-microscope/
Additional notes from the day
Excellent resources provided by Science and Plants for Schools (www.saps.org.uk) based at Cambridge
Botanic Garden.
Complete book of the Microscope by Bines et al. 2012 (Usbourne Internet-linked Reference Books) is a
good practical guide for beginners and includes information on commonly available stains etc.
Great idea to get kS1/KS2 pupils really looking at plants: create a name for a given tree/plant specimen
based on the observable characteristics of that plant e.g. the spiky, hairy, fairy forest tree.
Dr David Perkins
Using microscopes to view life in ponds/puddles/pools of water collected from under water fountains etc is
a great way to demonstrate the tenacity of life.
LEEF Training event: Using microscopes with children and young people
Start off with a general introduction to lenses: glasses and eyes, get pupils to experiment with focal length
by bringing their finger tips towards their noses: too far away and finger is not clear ditto too close,
somewhere en route is just right.
Use a 50cm ruler or informal scale to demonstrate magnification i.e. this millimetre will be represented by
4cm if magnified 40x; 40cm if magnified 400x etc.
Great advantage of monocular microscopes is to allow children to draw what they see simultaneously with
viewing it. Or if projecting the image on a large screen get them to draw in the dark to emphasise the
connection of brain, eye and hand.
Circular paper: draw what you see in the microscope view.
Microscopic water creatures can be observed to exhibit all the characteristics of living things under the
lens: they feed, excrete, reproduce (visible egg sacs), panic, sense one another and take evasive action etc.
Great route in to discuss the characteristics of living things and the importance of animal welfare and
concern for creatures less than 1mm long.
Ideally have a photo /model of some of the creatures you are likely to find in pond water to be able to
point to specific features as you view them under the lens. This helps in the relatability of image to
specimen for younger pupils.
Diatoms: plants with silicaceous structure ‘plants with a glass skeleton’.
Ideas for extension work: “Poetry in a puddle” and spiral snail shell poems.
Small Freshwater Creatures by Olsen et al. 2001 (Natural History Pocket Guides) OUP is a good clear guide
to commonly occurring pondwater creatures.
Useful resources and guidance available at www.microscopy-uk.org
Dr June Chatfield
Microscopes, hand lenses and magnifying glasses are all about understanding and manipulating light.
Higher magnification is not necessarily better: depends on what you are trying to see.
Lower power spreads the available light; higher power concentrates the light. Higher magnification
microscopes may have a condenser to assist with the concentration of the available light.
To pick up the texture of a 3D specimen e.g. seed cases, use a low angle light source rather than incident
lighting from above.
Translucent specimens e.g. pond plants such as Elodea or mosses (1cell thick) benefit from being bottom lit
i.e. transmitted light under the microscope stage.
Colourless plant and animal tissues will require a stain: commercially available prepared slides will use
histochemical tests to colour different parts of the preparation different colours (because different
chemicals take up and react with the different chemicals present in the specimen e.g. lignin)
As a general rule, liverwort leaves don’t have a midrib but mosses do because they live in drier places so
need the extra rigidity provided by midrib structure (link to habitats and adaptation).
Dr Claire Wells
Emphasised that few primary school teachers are science graduates: this is one place where environmental
educators can add value.
If purchasing digital microscopes e.g. Digi blue, beware that software upgrades can render equipment
obsolete.
4 week project, 2 hours per week, ‘Stepping inside the cell’. Week 1 Elodea (no stain necessary), Week 2
onion skin (iodine stain, applied by adult supervisors, children in lab coats and goggles to comply with
school H&S concerns), Week 3 cheek cells (again, stain necessary and applied by adult supervisors).
Slides and cover slips set out ready. Children shown how to label upper side of slide and carry safely in first
session.
LEEF Training event: Using microscopes with children and young people
Target outcomes for project: pupils to understand what a cell is, main features of cell, key differences plant
and animal cells.