Paper 2 - LO4

What is the purpose of visual observation in biological samples?

To examine and record features using tools like hand lenses or magnifying glasses.

What is the typical magnification range of a hand lens?

Hand lenses typically contain one to three lenses with fixed magnification.

What is the maximum magnification of a light microscope?

Up to 2000x.

What are the advantages of using a light microscope?

Quick and easy to use, can observe living specimens in color, portable, and inexpensive.

What are the limitations of a light microscope compared to an electron microscope?

Lower magnification and resolution; requires a light source.

What is the resolution of a light microscope?

200 x 10^-2 m.

How do you calculate total magnification using a microscope?

Total magnification = eyepiece magnification x objective lens magnification.

What is a stage micrometer?

A microscope slide with an accurate scale etched on it for calibration.

What is the purpose of a graticule in microscopy?

To measure the size of specimens by comparing eyepiece divisions to known measurements.

What is the process to prepare a temporary slide of onion skin?

Slice the onion skin thinly, place it on a slide, and cover with a coverslip.

What are the advantages of electron microscopy over light microscopy?

Higher magnification (up to 500,000x) and resolution (down to 2nm).

What is a significant disadvantage of electron microscopy?

Cannot observe living specimens due to the vacuum requirement.

What is the difference between transmission electron microscopy (TEM) and scanning electron microscopy (SEM)?

TEM transmits electrons through a specimen, while SEM detects secondary electrons from the surface.

Why is SEM preferred for 3D imaging of samples?

SEM provides greater depth of field and topographical information about the sample surface.

What is the role of X-rays in examining biological structures?

X-rays reveal hidden structures like bones by passing through the body and being absorbed at different rates.

How do ultrasound scans work?

Ultrasound uses high-frequency sound waves to create images of internal structures, safe for use.

What types of structures can ultrasound examine?

Structures that are difficult to access, such as during pregnancy observations.

What is the limitation of ultrasound imaging?

Cannot produce clear images of structures surrounded by bone, air, or gas.

What is the significance of using blue light in microscopy?

Blue light has the shortest wavelength (400nm), providing the sharpest images.

What is the field of view in light microscopy?

The area visible through the microscope, which is generally large for light microscopes.

What is the calibration factor in microscopy?

The ratio of eyepiece divisions to stage micrometer divisions, calculated for each objective lens.

What is the typical resolution limit of light microscopes?

About 200nm due to the wavelength of visible light.

What are the key features to identify in an onion skin slide?

Cell structure, including cell walls and nuclei.

What is the purpose of preparing a slide of lung tissue?

To observe and identify the cellular structure and function of lung cells.

What is the main advantage of using light microscopy for biological samples?

Ability to observe living specimens in their natural color.

What is the disadvantage of the small field of view in electron microscopy?

Limits the ability to observe the full width of larger samples.

What is the significance of using a fine focusing knob on a microscope?

To achieve a sharp image of the specimen after initial focusing.

What is the main function of the coarse focusing knob?

To bring the objective lens close to the slide for initial focusing.