Microscopy Fundamentals

Microscopy

• A microscope is an instrument used to view objects too small for the naked eye.
• Light microscopes use visible light to produce magnified images.
• Electron microscopes use a beam of electrons as illumination.

Key Terms

• Magnification is the enlargement of an object.
• Resolution is the ability of a microscope to distinguish between two closely spaced objects.

Light Microscopes

• Ideal for viewing live cells and large structures like nuclei or chloroplasts.
• Easy to use, can view live specimens, and is inexpensive.
• Lower magnification and resolution, unable to view smaller organelles like ribosomes or membrane structures.

Electron Microscopes

• Much higher magnification and resolution.
• Cannot view live specimens, expensive, and requires expertise to operate.

Differences Between Light and Electron Microscopes

• Electron microscopes are more expensive.
• Light microscopes show color, electron microscopes show black and white.
• Specimens must be dead to view under an electron microscope, whereas they can be alive or dead for light microscopes.

Parts of a Light Microscope

• Eyepiece Lens: The lens you look through, typically has a magnification of 10x.
• Objective Lenses: Multiple lenses with varying magnifications, such as low, medium, and high power.
• Stage: The platform where the slide with the specimen is placed.
• Stage Clips: Secure the slide in place.
• Coarse Focus Knob: Makes large adjustments to the focus.
• Fine Focus Knob: Makes small adjustments to focus.
• Diaphragm: Controls the amount of light reaching the specimen.
• Light Source: Provides illumination for viewing the specimen.
• Base: The bottom of the microscope, providing stability.
• Arm: Connects the base to the body tube, provides support.

Calculating Magnification

• The total magnification is calculated by multiplying the magnification of the eyepiece lens by the magnification of the selected objective lens.
• For example, an eyepiece lens with 10x magnification and a high-power objective lens with 40x magnification would result in a total magnification of 400x (10x * 40x = 400x).

Standard Form (Scientific Notation)

• Standard form is used to express very large or very small numbers in a concise way.

• It follows the format: (number between 1 and 9) x 10 ^ (power of 10).

• The power of 10 indicates how many places the decimal point has been moved.

• For example:

  • 1,000,000 (one million) can be written in standard form as 1.0 x 10^6.
  • 1,000,000,000,000,000,000,000,000,000,000 can be written in standard form as 1.0 x 10^27.