GCSE Biology Revision "Required Practical 1: Microscopes"
Summary
TLDRThis educational video offers a detailed guide on using an optical microscope to examine cells on a prepared slide, a crucial practical skill for students. It covers the microscope's parts, including the stage, objective lenses, and focusing dials. The tutorial demonstrates how to place the slide, adjust the lenses for clarity, and calculate total magnification. It also explains how to observe and sketch animal and plant cells, highlighting visible structures like the nucleus, cytoplasm, and cell membrane, and includes tips for adding a magnification scale to drawings.
Takeaways
- 🔬 The video is a tutorial on using an optical microscope to examine cells on a prepared slide, which is a required practical for exams.
- 📚 It's important to learn the details of the microscope's parts and their functions, as this could be a six-mark essay question in exams.
- 🔍 The microscope has a stage to place the slide, with clips to hold it, and a light source or mirror to illuminate the slide.
- 👀 The objective lenses, usually with magnifications of 4x, 10x, or 40x, are crucial for initial observation of the slide.
- 🔎 The eyepiece contains a lens with a 10x magnification, used in conjunction with the objective lens for viewing.
- 🔄 To view a slide, start by placing it on the stage, selecting the lowest power objective lens, and adjusting the coarse focusing dial.
- 🚫 When adjusting the objective lens, do not look through the eyepiece to avoid damaging the slide.
- 🔬 After initial focus, use the fine focusing dial to bring the cells into sharp view.
- 📈 Total magnification is calculated by multiplying the magnification of the eyepiece lens by that of the objective lens.
- 📝 For animal cells, you should be able to see the nucleus, cytoplasm, and possibly mitochondria, but not ribosomes.
- 🌿 For plant cells, expect to see the cell wall, cytoplasm, nucleus, and possibly the vacuole and chloroplasts.
- 📊 Include a magnification scale in your drawings, measured by placing a clear plastic ruler over the stage and showing the field of view diameter in millimeters.
Q & A
What is the main purpose of the video?
-The main purpose of the video is to teach viewers how to use an optical microscope to observe cells on a prepared microscope slide, which is a required practical that could appear as a six mark essay question in an exam.
What are some variations in the design of optical microscopes mentioned in the video?
-The video mentions that some optical microscopes may have a lamp instead of a mirror beneath the stage to illuminate the slide, and that the number and magnification of objective lenses can vary.
What is the function of the stage on a microscope?
-The stage is the central part of the microscope where the microscope slide is placed, and it often has clips to hold the slide in place.
What is the purpose of the objective lenses on a microscope?
-The objective lenses are used to magnify the specimen on the slide. Most microscopes have three different objective lenses with varying magnifications, typically four times, ten times, or forty times.
What is the magnification of the eyepiece lens in the video?
-The eyepiece lens in the video has a magnification of ten times.
How do you calculate the total magnification when using a microscope?
-The total magnification is calculated by multiplying the magnification of the eyepiece lens by the magnification of the objective lens in use.
What is the first step in using an optical microscope to view a prepared slide?
-The first step is to place the slide onto the stage and use the clips to secure it in place.
Why is it important to adjust the microscope from the side when the objective lens is close to the slide?
-Adjusting the microscope from the side helps prevent damage to the slide from accidentally touching the objective lens while looking through the eyepiece.
What is the role of the coarse and fine focusing dials in viewing a slide?
-The coarse focusing dial is used to increase the distance between the objective lens and the slide until the cells come into focus. The fine focusing dial is then used to bring the cells into a clearer focus.
What details can typically be observed in animal and plant cells under an optical microscope?
-In animal cells, one can typically observe the nucleus, cytoplasm, and cell membrane, with possible indications of mitochondria. In plant cells, the cell wall, cytoplasm, nucleus, and possibly the vacuole and chloroplasts can be seen.
How can you include a magnification scale in your drawing of the cells observed under the microscope?
-A magnification scale can be included by placing a clear plastic ruler over the stage, measuring the diameter of the field of view in millimeters, and then representing this measurement on the drawing with a scale bar,标注着相应的放大倍数, such as 100 times.
Outlines
🔬 Introduction to Using an Optical Microscope
This paragraph introduces the video's focus on teaching viewers how to use an optical microscope to examine cells on a prepared slide, a skill crucial for a required practical that could be assessed in an exam. The presenter briefly mentions the microscope's components, including the stage, objective lenses, eyepiece, and focusing dials, and notes that variations exist among microscope models, such as the presence of a lamp or mirror for light reflection.
Mindmap
Keywords
💡Optical Microscope
💡Prepared Microscope Slide
💡Stage
💡Lamp
💡Mirror
💡Objective Lenses
💡Eyepiece
💡Coarse Focusing Dial
💡Fine Focusing Dial
💡Magnification
💡Nucleus
💡Cell Wall
💡Scale Bar
Highlights
Introduction to using an optical microscope for examining cells on a prepared slide, a required practical for exams.
Explanation of the optical microscope's parts, including the stage, clips, and light source.
Differences in optical microscopes, such as the presence of a lamp or mirror for light reflection.
Description of the objective lenses with varying magnifications and their role in cell observation.
The function of the eyepiece lens and its magnification power in conjunction with the objective lens.
Demonstration of how to place a microscope slide on the stage and secure it with clips.
Guidance on selecting and positioning the lowest power objective lens for initial focusing.
Importance of adjusting the coarse focusing dial while observing from the side to prevent slide damage.
Process of using the coarse and fine focusing dials to bring cells into clear focus under the microscope.
Calculation of total magnification by multiplying the magnifications of the eyepiece and objective lenses.
Observation of animal cells under the microscope and the expected visibility of cellular structures.
Limitations of optical microscopes in observing fine details such as ribosomes.
Differences in viewing plant cells, including the visibility of the cell wall, cytoplasm, and nucleus.
Technique for creating a scale bar on drawings to represent the magnification and field of view.
Instructions on making a clear label drawing of observed cells with the inclusion of magnification.
Availability of practice questions on this required practical in the accompanying workbook.
Encouragement to click on the provided link to access additional resources for learning.
Transcripts
[Music]
I'm welcome back to three sighs lessons
cold okay by the end of this video you
should be able to describe how to use an
optical microscope to look at cells on a
prepared microscope slide um this is a
required practical so it's important
that you learn the details this could
come up in the exam as a six mark essay
question
okay I'm showing you here an optical
microscope and you should have used one
of these at school now I should point
out that some optical microscopes are
slightly different to this and I'll
discuss that in a minute I'm going to
take you through the important part of
the optical microscope and then we'll
discuss how to use it to view a
microscope slide and again you need to
learn the names of the different parts
the center of the microscope has a stage
this is where we place a microscope
slide the stage has clipped to hold the
slide in place below the stage there's a
lump light from the lump passes up
through the microscope slide now as I
said before some optical microscopes are
slightly different to this rather than
having a lamp these microscopes have a
mirror beneath the stage the mirrors
used to reflect light up through the
microscope slide okay above the stage
we've got a set of lenses these are
called the objective lenses most
microscopes have got three different
objective lenses these usually have a
magnification of four times ten times or
forty times at the top of the microscope
we've got the eyepiece and this is where
we look through the eyepiece contains
the eyepiece lens and that's got a
magnification of ten times the final
parts of the microscope or the course
focusing dial the fine focusing dial and
we'll be discussing how to use these
later
okay so we're gonna look now how to use
an optical microscope to view a prepared
slide first we place the slide onto the
stage and use the clips to hold the
slide in place we then select the lowest
power objective lens this is usually
four times we need to position the
objective lens so it almost touches the
microscope slide to do that we slowly
turn the cause focusing dial now it's
really important that we look at the
microscope from this side while we
adjust the position of the objective
lens when the objective lens almost
touches the slide we stop turning the
dial if we look through the eyepiece
while position in the objective lens
there's a risk that we damage the slide
okay at this stage we look down through
the eyepiece now we need to slowly turn
the course focusing dial this increases
the distance between the objective lens
on the slide we do this until the cells
come into focus at this stage we use the
fine focusing dial to bring the cells
into a clear focus okay now to calculate
the total magnification we multiply the
magnification of the eyepiece lens by
the magnification of the objective lens
the eyepiece lens has a magnification of
ten times and the low-power objective
lens has a magnification of four times
multiplying ten by four gives a total
magnification of 40 times at this point
we can select a higher power objective
lens for example 10 times again we'll
need to adjust the fine focusing dial to
bring the cells back into focus
so if we're looking at animal cells we
should see something like this I should
point out that this will depend on the
type of animal cell on the slide at this
stage we can use a pencil to make a
clear label drawing of some of the cells
now using an optical microscope we can
only see limited detail we can see the
nucleons the cytoplasm and the cell
membrane and these tiny flecks may be
mitochondria
however we definitely cannot see wiper
Solms if we look at plant cells we might
see something like these but again this
depends on the type of plant cells on
the slide under the light microscope we
should be able to see the cell wall the
cytoplasm and the nucleus we may also be
able to see the vacuole under
chloroplasts now on your drawing you
should also include a magnification
scale to do this we place a clear
plastic ruler over the stage and we
measure the diameter of the field of
view in millimeters then we show this on
a drawing using a scale bar you should
also write the magnification for example
100 times remember you'll find plenty of
questions on this required practical in
my vision workbook and you can gather
that by click on the link above
you
[Music]
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