Introduction to Microscopy

Objectives

• Learn to use a compound microscope correctly.

• Diagram the path of light through a compound microscope.

• Name major parts of a compound microscope.• Identify three basic morphologies of bacteria.

Size in Microbial World

Magnification

•Refraction (bending) of light as it passes through the lens produces magnified image•Two sets of lens contribute to total magnification •Four objective lenses: 4x (scanning), 10x (low power), 40-45x (high power), 100x (oil immersion).•Ocular lens: 10x

Resolution Wavelength of light usedResolving Power = 2 x numerical aperture

Qualities of a Good Image

Brightness - related to NA. Focus - related to Focal Length.

Resolution - related to NA & λ. Contrast - related to illumination (can be improved)

Focusing and Iris Diaphragm