Types of Microscopes

Types of Microscopes

• Optical Microscopes: Use light and lenses for magnification
  • Compound Microscopes: Utilize multiple lenses for high magnification
  • Stereo Microscopes: Provide a 3D view and used for lower magnification
• Electron Microscopes: Employ electron beams instead of light, achieving significantly higher magnifications
  • Transmission Electron Microscopes (TEM): Pass electrons through thin specimens
  • Scanning Electron Microscopes (SEM): Scan the surface of specimens with electron beams
  • Scanning Probe Microscopes: Utilize physical probes to scan surfaces on an atomic level

Anatomy of a Light Microscope

• Eyepiece (Ocular Lens): The lens you look through, typically providing 10x or 15x magnification
• Objective Lenses: Multiple lenses on a rotating nosepiece, each with different magnification levels (e.g., 4x, 10x, 40x, 100x)
• Revolving Nosepiece: Holds and allows selection of different objective lenses
• Stage: Platform where the slides are placed, often with clips or a holder to secure the slide.
• Stage Clips: Secure the slide to the stage.
• Condenser: Lens system below the stage focusing light onto the specimen.
• Diaphragm (Aperture Iris): Controls the amount of light passing through the specimen, located beneath the condenser.
• Illuminator (Light Source): Provides the light needed for imaging, usually a built-in lamp or LED.
• Base: Bottom part providing stability and housing the illuminator.
• Arm: Connects the base to the body tube, supporting optical components.
• Coarse Focus: Adjusts focus by moving the stage or lenses.
• Fine Focus: Allows precise fine-tuning of the focus.
• Body Tube: Connects the eyepiece to objective lenses, maintaining alignment.

Magnification

• Magnification: Enlarging the appearance of an object for detailed examination
• Objective Lenses: Primary lenses near the specimen, providing initial magnification (common magnifications: 4x, 10x, 40x, 100x)
• Eyepiece (Ocular Lens): Further magnifies the image from the objective lenses (typical magnifications: 10x or 15x)

Resolution

• Resolution: Ability to distinguish two closely spaced points as separate entities
• Resolving Power: A microscope's ability to distinguish fine details, inversely related to the minimum resolvable distance (higher resolving power = seeing finer details)

Field of View (FoV)

• Field of View: Diameter of the visible area through the eyepiece
• Relationship between Magnification and Field of View: As magnification increases, the field of view decreases.
• Typical Field of View Sizes: Larger view with lower magnification (scanning), smaller view with higher magnification (high-power)

Using a Microscope

• Begin with the scanning objective lens
• Place the specimen in the center of the field of view
• Focus using the coarse knob
• Fine-tune focus with the fine knob
• Switch to low power and repeat focusing steps 3-4
• Switch to high power and use ONLY the fine adjustment knob for focusing
• Always start with the scanning objective
• Store the microscope with the scanning objective in place and cord wrapped around
• Carry with both hands, base and arm

Wet Mounts

• Wet Mount Technique: Prepares a specimen for viewing under a microscope by placing it in a drop of liquid on a slide and covering with a cover slip.
• Purpose: Observing living organisms or specimens in their hydrated state.
• Steps:
  • Clean slide
  • Drop of liquid (water, saline, staining solution)
  • Add specimen (small piece or crushed if large)
  • Apply cover slip at 45 degrees to avoid air bubbles
  • Spread evenly
  • Examine under microscope, starting with low-power lens

Staining Specimens

• Purpose: Improving visibility of cell parts
• Common Stain: Iodine
• Steps:
  • Drop of Stain on slide
  • Specimen centered on stain
  • Cover slip applied

Onion Cell Wet Mount

• Steps:
  • Obtain clean slide and cover slip
  • Cut small piece of onion
  • Peel inner surface (tissue-like)
  • Place onion on slide
  • Add drop of iodine
  • Cover with cover slip
  • Observe under microscope
  • Describe observations

Cheek Cell Wet Mount

• Steps:
  • Clean Slide, coverslip, and toothpick
  • Gently scrape inside cheek with toothpick
  • Place scrapings on slide
  • Add drop of stain (methylene blue)
  • Coverslip applied
  • Observe under microscope

Microscope Quiz

• Start with the scanning objective.
• Use fine adjustment knob when using high power objective.
• Type used in most science classes is the compound microscope.
• The diaphragm controls the amount of light.
• Carry by the base and arm.
• Objectives are attached to the revolving nosepiece.
• Always store with the scanning objective in place.
• Total magnification is the ocular magnification multiplied by the objective lens magnification.

Explore the various types of microscopes including optical and electron microscopes. Learn about the anatomy of a light microscope and how different lenses contribute to magnification. This quiz will test your knowledge of microscopic technology and its applications.