Microscopes in A Level Biology

These flashcards cover key concepts related to microscopes, including types, magnification, resolution, calibration, and practical applications in biology.

What are the three key types of microscopes?

Optical microscope, transmission electron microscope, and scanning electron microscope.

What does magnification refer to in microscopy?

Magnification refers to how many times larger the image is compared to the actual size of the object.

Define resolution or resolving power in microscopy.

Resolution is the minimum distance between two objects that can still be viewed as separate.

What is the primary light source for an optical microscope?

A beam of light released by a lamp or reflected by a mirror.

Why can't living samples be viewed under an electron microscope?

Living samples can't be viewed because electron microscopes require a vacuum, which prevents air from interacting with the sample.

What is the difference in resolution between optical and electron microscopes?

Electron microscopes have higher resolution due to the shorter wavelength of electrons compared to light.

What type of images do optical microscopes produce?

Optical microscopes produce color images.

How does the wavelength of light affect the resolution of optical microscopes?

A longer wavelength of light results in lower resolution.

What is the formula for calculating magnification in microscopy?

Image size = Actual size x Magnification.

What is an eyepiece graticule?

A glass disc with a scale etched onto it, used to measure the size of objects viewed under a microscope.

Why is it necessary to calibrate the eyepiece graticule?

To account for different magnifications affecting the value of divisions on the eyepiece graticule.

What do stage micrometers measure?

Stage micrometers measure distances in micrometers.

How many micrometers are there in one millimeter?

There are 1,000 micrometers in one millimeter.

What image quality do scanning electron microscopes provide?

Scanning electron microscopes provide three-dimensional images.

What happens to the electron beam in a transmission electron microscope?

Some electrons are absorbed by the specimen while others pass through, creating an image based on the varying absorption.

What is the actual size represented by a scale bar of 50 micrometers?

The actual size represented by the scale bar is 50 micrometers.

What is the significance of using a millimeter ruler for measuring images in microscopy?

The image size measured in millimeters needs to be converted to micrometers for calculations.

What is the value of one division on a stage micrometer in the given example?

One division on the stage micrometer is worth 10 micrometers.

How do you convert millimeters to micrometers?

Multiply the number of millimeters by 1,000.

What ratio of divisions was found in the eyepiece graticule to the stage micrometer in the example?

A ratio of two divisions from the eyepiece to one division of the stage micrometer.

If one division of the eyepiece graticule is worth 5 micrometers, how many divisions cover a nucleus measuring 13 divisions?

The nucleus is 65 micrometers long.

What must you do to the image size and actual size before using them in the magnification formula?

Both sizes must be in the same unit.

What kind of samples can light microscopes view that electron microscopes cannot?

Light microscopes can view living samples.

What type of images does the transmission electron microscope generate?

Transmission electron microscopes generate two-dimensional black and white images.

What is the primary function of the stage micrometer during calibration?

To provide a known scale against which the eyepiece graticule can be calibrated.

What is the magnification if an image size is 20 millimeters and the actual size is 50 micrometers?

The magnification is 400 times.

Can you see organelles in detail with an optical microscope?

No, optical microscopes cannot see organelles in detail due to lower resolution.

How do optical microscopes create images?

By shining a beam of light through the specimen and using lenses to magnify the image.

What is one disadvantage of black and white images produced by electron microscopes?

They do not show real colors of the specimens.

What key feature differentiates scanning electron microscopes from transmission electron microscopes?

Scanning electron microscopes reflect and scatter electrons off the specimen surface to create 3D images.

What is the purpose of counting divisions on the eyepiece graticule during calibration?

To determine how many divisions fit into the length of one division on the stage micrometer.

What are the limitations of optical microscopes compared to electron microscopes?

Optical microscopes have lower resolution and magnification.

What is the calibration process of the eyepiece graticule based on?

It is based on how different objective lenses magnify the image.

What happens to the eyepiece graticule value when changing magnifications?

The value of one division on the eyepiece graticule changes with different magnifications.

What type of calculations are considered skills from GCSE linked to magnification?

Rearranging the magnification formula and converting units.

Why is it important to use an eyepiece graticule in microscopy?

To measure the actual size of objects accurately at different magnifications.

Explain how to calculate actual size using the eyepiece graticule.

Multiply the number of divisions covered by the specimen by the value per division determined through calibration.

What does the eyepiece graticule help visualize?

It helps visualize how many divisions a given cell structure occupies.

What is the importance of understanding cell fractionation and ultracentrifugation in microscopy?

These methods help scientists discover the internal structures of cells, but they are not the focus in this session.

What is the primary educational purpose of the video by Miss Estrich?

To teach key concepts about microscopes, magnification calculations, and calibration techniques for biology students.

How can you practice your understanding of these microscopy concepts?

By reviewing the linked videos for additional explanations and examples.

What key point is emphasized regarding electron microscopes?

They provide higher magnification and resolving power, allowing for detailed imaging of organelles.

Summarize the overall topic of this lecture session.

The focus is on understanding different types of microscopes, how to calculate magnification, and the calibration process of eyepiece graticules.

What skills linked to microscopy can be developed through this topic?

Math skills for magnification and conversions, as well as practical skills for using microscopes.