Microscopes: Simple vs. Compound

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.