Introduction to the Microscope

Introduction to the Microscope

• A microscope is a device that magnifies and displays an object's image.
• Microscopes can improve resolution, contrast, and magnification.
• The human eye can resolve objects around 0.1 mm, a light microscope can resolve 0.2 µm (with 1000x magnification), and an electron microscope can resolve objects 0.1 nm.
• The first microscope was invented by Zacharias Jansen, a Dutch spectacle maker, around 1595.

History of the Microscope

• Robert Hooke used a microscope to observe a thin slice of cork and called the small compartments “cells,” which he believed were the smallest units of life.
• Anton van Leeuwenhoek, considered the "Father of Microscopy," built over 500 microscopes.
• He was the first to view microorganisms through a microscope, observing a drop of pond water filled with life - "tiny animalcules."
• In 1932, Frits Zernike invented the phase-contrast microscope, which allowed the study of colorless and transparent biological materials.
• Ernst Ruska co-invented the electron microscope in 1931.
• The invention of the scanning tunneling microscope in 1981 by Gerd Binnig and Heinrich Rohrer allowed for detailed 3D images of objects down to the atomic level.

Parts of the Microscope

• Body Tube: Connects the lenses and maintains a fixed distance between them.
• Rotating Nosepiece: Allows for switching between different objective lenses.
• Objective Lenses: Multiple lenses with different magnifications (often 4x, 10x, 40x).
• Stage Clips: Hold the slide securely in place.
• Diaphragm: Regulates the amount of light passing through the specimen.
• Light Source: Provides illumination for viewing the specimen.
• Ocular Lens: The lens nearest the observer, typically with a 10x magnification.
• Arm: Connects the body tube to the base.
• Stage: The flat surface where the slide is placed.
• Coarse Adjustment Knob: Moves the stage up and down rapidly for initial focusing.
• Fine Adjustment Knob: Precisely adjusts the stage for sharper focus.
• Base: The stable foundation of the microscope.

Magnification and Resolution

• Magnification is the degree of enlargement of the image.
• Total magnification is calculated by multiplying the ocular lens magnification by the objective lens magnification.
• Resolution: The clarity of an image, or the ability to distinguish two closely spaced points.

Types of Microscopes

Light Microscopes

• Uses light to illuminate and magnify specimens.

• The two main types of light microscopes are:

  Bright-field Microscope

• The most common type.

• Projects a dark image against a brighter background.

• The objective lens forms a real image, which is then further magnified by the ocular lens.

  Dark-field Microscopy

• Illuminates the specimen in a way that only reflected or refracted light from the specimen reaches the objective lens.

• Produces a brightly illuminated specimen against a dark background.

  Phase-contrast Microscope

• Converts small differences in refractive index and density into variations in light intensity.

• Allows for viewing transparent and unstained specimens.

  Fluorescence Microscope

• Uses fluorochromes (dye molecules) that fluoresce under specific wavelengths of light.

• Creates images based on fluorescent signals from the treated specimen.

Electron Microscopes

• Uses a beam of electrons for illumination and magnification.
• Offers greater resolution than light microscopes.
• Requires a vacuum chamber for electron beam operation.
• Cannot be used to view living specimens.

Types of Electron Microscopes

• Transmission Electron Microscope (TEM):

  • Uses electrons that pass through a very thin slice of the specimen.
  • Creates highly magnified 2D images.

• Scanning Electron Microscope (SEM):

  • Scans the surface of the specimen with a focused electron beam.
  • Produces detailed 3D images.

Rules for Using a Microscope

• Always carry the microscope with one hand on the arm and the other under the base.
• Turn on the light source before placing the slide.
• Secure the slide with stage clips.
• Keep the stage and slide dry.
• Start with the lowest objective lens (4x) and focus using the coarse adjustment knob.
• Slowly switch to higher objective lenses (10x and 40x).
• Use the fine adjustment knob only for high-power lenses.
• Lower the stage before switching back to the low-power lens.
• Turn off the light source, unplug the microscope, and cover it before storing.

Preparation of a Slide: Wet Mount

• Place the specimen in the center of a clean slide.
• Add a large drop of water over the specimen.
• Hold a coverslip at a 45-degree angle and gently lower it onto the water drop.
• Avoid air bubbles.

This quiz explores the fundamentals of microscopes, including their history, functionality, and the pioneering figures behind their development. You will learn about resolution, magnification, and significant milestones in microscopic technology. Test your knowledge on how microscopes have advanced our understanding of the microscopic world.