12 Questions
What is the main purpose of microscopy technology?
To visualize things that are too small to be seen by our naked eyes
Who is credited with the invention of the first microscope?
Zacharias Janssen
What is the ability of a microscope to make small objects seem larger?
Magnification
What determines the resolving power of a microscope?
The wavelength of the light source used
Why may an object be seen as one if the wavelength is too long to pass within the space of two closely located objects?
Because the objects are too close together
What was the quality of the first microscope developed by Zacharias Janssen?
Poor quality
Who developed the improved compound light microscope in the 1830s?
Joseph Jackson Lister
What is the primary function of the ocular lens in a compound microscope?
To magnify the image formed by the objective lens
What is the purpose of the coarse focusing knob in a compound microscope?
To moves the stage up and down for focusing
What is the minimum power of the objective lens in a standard compound microscope?
4X
Why is immersion oil required for the 100X oil immersion lens in a compound microscope?
To prevent light from refracting when it travels through material with different index of refraction
What is the primary function of the condenser in a compound microscope?
To focus light through the specimen
Study Notes
Microscopy
- Microscopy is a technology that enables the visualization of objects too small to be seen by the naked eye.
- The birth of microbiology is attributed to the invention of the first microscope by Antonie van Leeuwenhoek.
Magnification and Resolution
- Magnification is the ability to make small objects seem larger, such as making a microscopic organism visible.
- Resolution is the ability of a microscope to identify two objects located closely as two discrete units.
- Resolving power depends on the wavelength of the light source used in a microscope.
- A shorter wavelength of light allows for better resolution.
Compound Light Microscope
- The first compound light microscope was developed by Zacharias Janssen in 1600, but it was of poor quality and could not see bacteria.
- Joseph Jackson Lister improved the compound light microscope in the 1830s, which is the basis for modern microscopes.
- Compound light microscopes use visible light as a source of illumination and have two lenses: an ocular lens and an objective lens.
Compound Light Microscope Components
- Arm: supports the microscope when it is carried.
- Base: the bottom part that supports the whole microscope.
- Ocular lens (eyepiece): re-magnifies the image formed by the objective lens, usually with a 10X or 15X power lens.
- Body tube: connects the eyepiece to the objective lenses and transmits the image.
- Objective lenses: primary lenses that magnify the specimen, usually with three to four lenses ranging from 4X to 100X.
- Stage: holds the microscope slide in position.
- Condenser: focuses light through the specimen.
- Diaphragm: controls the amount of light entering the condenser.
- Coarse focusing knob: moves the stage up and down for focusing.
- Fine focusing knob: moves the stage slightly to sharpen the image.
Objective Lenses
- Scanning objective lens: 4X magnification.
- Low power objective lens: 10X magnification.
- High power objective lens: 40-45X magnification.
- Oil immersion lens: 95-100X magnification, requires the use of oil immersion to produce a clear image.
Oil Immersion
- Oil immersion is required for 100X oil immersion lens to produce a clear image.
- Immersion oil has a refractive index of 1.51, which is close to the refractive index of coverslips.
- Immersion oil prevents the light from refracting, giving a clear image.
Explore the world of microscopy, its types, and its impact on the development of microbiology. Learn about the inventors and the key concepts of magnification and resolution.
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