10 Questions
What is the total magnification when using a X10 ocular lens and a X40 objective lens on a compound light microscope?
X400
How would replacing the condenser with a darkfield condenser impact the view in a compound light microscope?
Objects will be observed against a dark background.
What are photomicrographs?
Photographs taken through the lens system of a compound light microscope.
What term is used to refer to the microscope when objects are observed against a bright background?
Brightfield microscope
Which component in a compound light microscope impacts whether objects are seen against a dark or bright background?
Condenser
If an X10 ocular lens is used with an X100 objective lens, what is the total magnification achieved?
X1000
What is the role of the eyepiece or ocular lens in a compound light microscope?
To magnify the image further for observation.
What is the resolving power of a compound light microscope?
The ability to distinguish two separate points as distinct entities
What is one of the limitations of visible light in microscopy?
Its inability to penetrate thick specimens effectively
What happens when an object is observed under dark field illumination in a microscope?
The object appears brighter against a dark background.
Study Notes
Simple Microscopes
- Contain only one magnifying lens
- A magnifying glass is an example of a simple microscope
- Images appear 3-20 times larger than the object's actual size
- Leeuwenhoek's simple microscopes had a maximum magnifying power of about X300 (300 times)
Compound Microscopes
- Contain more than one magnifying lens
- Also referred to as compound light microscopes due to the use of visible light as the source of illumination
- Usually magnify objects about 1000 times
- Resolving power is approximately 0.2 µm (about 1,000 times better than the unaided human eye)
- Limited by the wavelength of visible light (~0.45 µm), which determines the minimum size of objects that can be seen
Improving Contrast in Light Microscopy
- Contrast improvement is essential for a clear final image
- Staining is a common method to improve contrast in bright field microscopy
- Dyes used for staining are organic compounds that bind to specific cellular materials
- Basic dyes are positively charged and bind to negatively charged components like nucleic acids and acidic polysaccharides
- Staining can, however, kill cells and distort their features
Types of Staining Procedures
- Simple stain
- Differential stain
- Structural stains
Electron Microscopes
- Enable the observation of extremely small microbes like rabies and smallpox viruses
- Cannot be used to observe living organisms, as the processing procedures are lethal to cells
- Use an electron beam as the source of illumination and magnets to focus the beam
- Have a much higher resolving power than compound light microscopes
- Come in two types: transmission and scanning electron microscopes
Learn about the differences between simple microscopes, which contain only one magnifying lens, and compound microscopes, which contain multiple lenses for higher magnification.
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