Chapter 2.pptx - How We See the Invisible World Chapter 2...

How We See the Invisible
World
Chapter 2

Ch. 2 Learning Objectives
1. Microscope History and Development
(van Leeuwenhoek vs. Hooke vs. Galileo)
2. Explain difference between transmission, reflection,
refraction
3. Explain how lenses are used in microscopy to manipulate
visible and ultraviolet (UV) light
4. Explain difference between magnification & resolution
5. Know the factors that affect resolution
6. Know different types and differences between
microscopes & electron microscopes
7. Describe basic procedures of staining techniques

Invisible, but not truly…
We can manipulate light for magnification to see microbes in
different ways

•
Mostly we view microbes through the visible light
spectrum
•
This light behaves as electromagnetic waves and has
same properties:

Wavelength – length between peaks

Amplitude – height of peaks

Frequency – rate of peaks in time
•
Longer wavelengths = lower frequency
2.1 The Properties of Light

Light waves interact differently with objects or other light waves:
1. Reflection - wave bounces off material
2. Absorbance – wave is captured
3. Transmission – wave travels through
2.1 The Properties of Light

4. Interference – interacts w/ another wave
5. Diffraction – wave is larger than object and scatters
6. Refraction – change direction and/or speed
2.1 The Properties of Light

•
Refraction is very important in microscopy
•
Microscopes use materials with different refractive
indices to achieve magnification
•
Refractive index – how much a material slows the
speed of light
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Example: Refractive Index of glass
= = 1.5
2.1 The Properties of Light

•
Lens use refraction to direct light to an image point
•
Convex lens are used to magnify; refraction occurs on a
curved boundary to meet a focal point (microscope)
•
Concave lens refracts light away from a focal point (reading
glasses)
2.1 The Properties of Light