Marsh, Parkes and Boulter
Children’s understanding of scale
Children’s understanding of
scale – the use of
microscopes
Gwyneth Marsh, Tessa Parkes and Carol Boulter
How do children interpret what they see through magnifying lenses
and microscopes?
The problem with magnifying lenses is that they are
not viewed as an everyday tool to enhance the
descriptive and explanatory skills of very young
scientists. In our experience young children are not
given them to work with very often. We don’t really
know what young children think they are looking at
when they view an object through a magnifier. Nor
do we know how they represent what they are seeing
in terms of its apparent and actual size.
During the last four years a small group of primary
teachers interested in researching their own practice
have been working together, investigating children’s
perception of various aspects of scale. They meet
within a larger research group, called MISTRE
(Models in Science and Technology, Research in
Education), based at Reading University. This larger
group is researching several aspects of the theory and
practice of models and modelling in science education
both inside and outside schools.
The MISTRE Primary Classroom Research Group
chose to look at aspects of scale for several reasons:
ABSTRACT
Children’s intuitive and actual understanding of
scale in relation to the use of magnifying
instruments is not well researched or
understood. Young children (5–11 year-olds) are
sometimes given magnifying lenses to look at
small objects. We assume that with minimal
tuition they are able to use these tools and
correctly interpret what they see. This study has
found that we may be making assumptions
which could have implications for both primary
and secondary school teachers.
■ there has been very little research on children’s
understanding of scale;
■ there is a tendency for teachers to gloss over the
scale aspect of representation of an object (in the
form of pictures, maps or verbal descriptions);
■ there is a tendency to assume that all will be taught
and understood in a few lessons which focus
specifically on scale;
■ many subjects other than science, such as
geography, art and maths, involve the use of scale
and more information about primary children’s
understanding of scale would be relevant in
teaching these subjects.
Aspects of scale investigated by the MISTRE Primary
Research Group range from ideas of distance and size
related to studies of the solar system, through the
relative sizes of familiar objects such as houses and
ourselves, to ideas about small objects and the use of
magnifiers and microscopes.
Previous research (Boulter, 1997) suggests that
children are intuitively able to imagine large and small
objects. They also appear to be able to understand the
relationship between a bridge span and a load.
However, attaching a specific unit of measurement
to these exercises was poorly performed. Without
measuring, children appear to be able to alter the
length of a line (increase or decrease its size by a given
factor) to a reasonable degree of accuracy. However,
when asked to estimate the length of a line, very few
8–13 year-olds were able to supply a reasonably
accurate figure. This was surprising in light of the
fact that children had been able to double and halve a
given line accurately. It was found that, with careful
and specific instruction with regard to scale, children
School Science Review, June 2001, 82(301)
27
Children’s understanding of scale
Marsh, Parkes and Boulter
Photo, Wanda Parkes, Herries School.
were able to enlarge and, less easily, decrease their
whole drawings accurately. It would appear that the
inclusion of numbers into the scaling task proves a
tremendous stumbling block.
Work with groups of young children with a range
of microscopes and magnifiers indicated that they may
not have a complete understanding of the mechanisms
of magnification. This led to an attempt to gain some
insight into their understanding of magnification. In
science club sessions and science lessons children
aged 5–12 have been observed to select, in the first
instance, the largest hand-lens with a handle (the
conventional ‘Sherlock Holmes’ shape), to observe
animals in leaf litter, seeds or pencils. A fair amount
of persistency is required to persuade the children to
use a smaller, more curved lens. The strongly curved
lens has a shorter focal length and needs to be held
closer to the eye, but the magnification is greater and
enables children to see the important microscopic
detail.
The working of so many things hinges upon the
microscopic structure of materials. For instance, a
closer look at newspaper, knitted or woven fabric,
wood, Velcro, glues and skin, gives many clues to
their structure and properties such as absorbency,
water-proofing, stickiness and heat-holding capacity.
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School Science Review, June 2001, 82(301)
This study focused on helping children to use
magnifiers to obtain a rewarding image and exploring
ways in which teachers can include accurate scale
representations in their lessons from the first instance
of using magnifiers.
Once the use of hand-lenses had been mastered,
the children moved on to binocular reflecting
microscopes. However, the children seemed unable
to persevere with trying to obtain a clear image and
tended to give up easily, claiming that the microscope
was not working, even though this type of microscope
is easily focused. It may be that the children’s young
eyes are more efficient than is realised, allowing them
to see as clearly with the naked eye as adults see with
a ×9 microscope (Evennett, 1997).
It is essential that early encounters with
microscopes are positive and rewarding. The ‘owning’
of a real microscope and the achievement of successful
focusing are positive aspects which allow the children
to engage enthusiastically with the observational task
set, such as counting legs and drawing heads of small
creatures. The skills acquired by using microscopes
successfully at this early age will be invaluable when
the children re-encounter the equipment in secondary
school science lessons, saving teaching time and
boosting the children’s confidence.
Marsh, Parkes and Boulter
The study
Children’s understanding of magnification was
investigated using static objects such as pencils,
pennies, salt crystals, seeds, fingers, newsprint and
fabric. In addition to finding out about their understanding of the mechanics of magnification – that the
lenses make the objects appear larger – and their
competence with the use of magnifiers, we had a
further objective. This was investigating children’s
understanding of and ability to apply quantitative
statements regarding scale, that is, to put a number to
the amount of magnification. For this part of the
investigation, microscopes, rather than hand-lenses,
were used. A number of electron-micrographs of
chromosomes, microchips, flea heads and skin flakes
were accessible to the children in the form of posters,
to promote discussion. Some of these carried scale
information. A series of posters including ‘Amazing
micro-organisms’ and ‘Blue-green algae’ (with wellmarked scales) were also available (see end for
sources).
Two groups of children aged 7–12 were asked to
look at a salt crystal with the naked eye and then
through a microscope (either ×9 or ×20) and estimate
how much larger the crystal appeared when viewed
through the microscope. Three children were common
to both groups.
Estimates ranged from twice as big to nearly 7
times larger. When asked to draw the crystal exactly
as they saw it through the microscope, the size of the
drawings varied a great deal, though generally the
children observing through a ×9 microscope drew a
smaller crystal than those using a ×20 microscope.
The same activity was repeated using a penny and a
pencil. Tracing around the penny provided a real-size
drawing, but the magnified view, in all but a few cases,
showed only a token enlargement.
A majority of the younger children (age 5–8) drew
a complete enlarged pencil or penny and not just the
part they saw through the microscope.
A circular frame was subsequently supplied for
the drawings to give the children a frame of reference
and to emphasise the comparison between the framing
circle and the circle of light that they saw though the
microscope. A plastic ruler slid on to the stage of the
microscope gave a measurement of the diameter of
the circle of the field of view (the circle of light). The
length of an object can also be measured this way.
Children’s understanding of scale
Suggestions for using microscopes
■ Do not lose the sense of wonder about small
things. It is easy to become too focused on a task
and marginalise the excitement.
■ Spend time looking at the small objects and
listening to children’s comments about them. Then
remind the children of the wonderful powers of the
magnifier, its uses, its workings and its limitations.
■ Use microscopes wherever possible as tools
to supplement observations of objects and
materials.
■ State the task very clearly and mention that
judgements of size need to involve ideas about
numbers and, for older children, scale. Point out
that if they have measured one thing it is not
sensible just to guess the next.
■ Practise using quantitative measures to
compare the sizes of everyday objects. This is
likely to improve children’s ability to judge relative
sizes of small items and increase their awareness
of scale.
Seed investigation
The children placed a seed under the microscope and
measured its actual length as well as the diameter of
the circle of light as described above. Then they were
each given a piece of paper with a large circle drawn
on it (the framing circle). They were asked to look at
their seed through the microscope and draw on the
paper what they saw. With one exception, the drawing
of the magnified image was larger than that of the
actual object, but the size of the majority of the
drawings was not in proportion to the size of the
framing circle.
There were small discrepancies in the actual size
of the seeds and some inaccuracies in measurement
of seed length, but the latter were easy to spot by
looking at the group results of ratio of actual seed
size to diameter of circle of light (which were
encouragingly consistent). The two ratios, that of
actual seed length to diameter of circle of light of the
microscope (A), and the length of the drawn image
of the seed to the diameter of the drawn circle (B),
were compared at each magnification (Tables 1 and
2). If the child had judged the enlargement accurately
these two ratios should have the same value (A:B = 1).
This would be when the children had drawn a
representation in the drawn circle which was the same
as the actual image in the circle of light.
Using the ×9 microscopes three of the eight
children judged well and their ratios were between 1
School Science Review, June 2001, 82(301)
29
Children’s understanding of scale
Marsh, Parkes and Boulter
Table 1 Children’s results using ×9 magnification.
Name
Age
(years)
Type of seed
Charlotte
7
Caitlin
7
Rebecca
7
Phoebe
8
Bernard
9
Charlotte
Helen
Sean
11
11
12
sesame
pepper
sesame
pepper
sesame
pepper
sesame
pepper
sesame
pepper
grass
grass
grass
Ratio of seed size Ratio of drawn
to diameter of light seed size to
circle (A)
diameter of
drawn circle (B)
0.15
0.25
0.10
0.20
0.10
0.15
0.16
0.55
0.15
0.20
0.35
0.35
0.35
0.15
0.13
0.12
0.07
0.13
1.00
0.01
0.16
0.06
0.10
0.20
0.15
0.21
Ratio of A to B
1.0
0.5
1.2
0.4
1.3
6.7
0.1
0.3
0.4
0.5
0.6
0.4
0.6
Table 2 Children’s results using ×20 magnification.
Name
Age
(years)
Type of seed
Jemma
7
Sam
7
Abi.F.
8
Natalie
Victoria
Jessica
8
8
9
Charlotte
Helen
Jodi
Sean
11
11
11
12
sesame
pepper
sesame
pepper
sesame
pepper
sesame
pepper
sesame
pepper
grass
grass
grass
grass
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School Science Review, June 2001, 82(301)
Ratio of seed size Ratio of drawn
to diameter of light seed size to
circle (A)
diameter of
drawn circle (B)
0.30
0.40
0.25
0.40
0.30
0.50
0.33
0.50
0.33
0.44
0.80
0.64
0.64
0.64
0.03
0.44
0.10
0.09
0.04
0.08
0.11
0.10
0.09
0.23
0.20
0.74
0.38
0.19
Ratio of A to B
0.1
1.1
0.4
0.2
0.1
0.2
0.3
0.2
0.3
0.5
0.3
1.2
0.6
0.3
Marsh, Parkes and Boulter
Children’s understanding of scale
and 1.3 (Table 1). Other children showed enlargement
of seeds related to circle enlargement over a range.
There was one unusually enlarged seed sketch which
increased the relationship by 6.7!
Those using more powerful magnification (×20)
were even less inclined to increase the size of the seeds
they drew in proportion to the diameter of the circle.
One of the older children’s drawings (age 11) was
comparable in size to the image, with a ratio of A:B
of 1.2 (Table 2).
Why this inability to draw small things like seeds,
markings on pennies and crystals magnified to scale?
Could it be that in a child’s mind the essence of a
seed is its tiny size and that this assumes paramount
importance, overriding the somewhat artificial view
of enlargement through a microscope?
It is highly unlikely that the children were unable
to judge the size of the crystals and the seeds. Previous
research has shown that young children are able to
draw lines double, half and a tenth the length of one
shown to them. Granted, the two-dimensional circle
is less easy to deal with than a line (Boulter, 1997).
However, the initial difficulties of using ruler
graduations viewed through a lens system to measure
the length of a seed and a light-circle diameter could
well have diverted attention from the object of the
exercise, and, having mastered the numerical task of
measuring and recording, the children may have
lapsed into the easy drawing of a seed as a small thing.
The fact that those children using ×20 magnification were given larger circles on their paper than most
of those using ×9 might have influenced the drawing
of seeds. This variation in circle size was an attempt
by the teacher/researcher to convey an impression of
uniqueness of each piece of work and so encourage
individuals to judge size for themselves.
References
Poster sources
Boulter, C. (1997) Aspects of primary children’s
understanding of scale. The New Bulmershe Papers.
University of Reading.
Amazing micro-organisms. Industry Supports Education,
sponsored by the Medical Research Council.
Evennett, P. (1997) Lenses and magnification. The Young
Detectives Magazine, 1(3). The Royal Microscopical
Society.
Conclusions
Working with very small objects and using magnifiers
in primary science lessons lays important foundations
for the development of concepts at key stage 3 in
science, from the understanding of particles to microorganisms. In our experience, primary teachers with
access to magnifiers tend to allow the children to use
them without considering what the children might
actually be seeing through the lens. Children need
guidance to interpret what they are seeing through
magnifiers. This guidance needs to take into account
the children’s intuitive understanding of scale and
magnification, enabling them to interpret magnified
images appropriately.
What can you see looking through a microscope? Times
Educational Supplement, March 1998.
Gwyneth Marsh is a class teacher (Y4) at Northwood College, Middlesex.
Carol Boulter is a lecturer in the School of Education, University of Reading.
Tessa Parkes teaches science at Herries Preparatory School, Cookham Dean, Berkshire.
School Science Review, June 2001, 82(301)
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Children’s understanding of scale
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School Science Review, June 2001, 82(301)
Marsh, Parkes and Boulter