Cell theory

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LESSON 3

Ch. 2 “Cells” Section 2: “Viewing Cells”

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Early Microscopes

Zacharias Janssen - made 1st compound microscope

a Dutch maker of reading glasses (late 1500’s)

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Leeuwenhoek

made a simple microscope (mid 1600’s)

magnified 270X

Early microscope lenses made images larger but the image was not clear

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Leeuwenhoek's microscope

A) a screw for adjusting the height of the object being examined

B) a metal plate serving as the body

C) a skewer to impale the object and rotate it

D) the lens itself, which was spherical

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Modern Microscopes

A microscope is simple or compound depending on how many lenses it contains

A lens makes an enlarged image & directs light towards you eye

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A simple microscope has one lens

Similar to a magnifying glass

Magnification is the change in apparent size produced by a microscope

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Compound Microscope

A compound microscope has multiple lenses

(eyepiece & objective lenses)

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Stereomicroscope

creates a 3D image

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Total Magnification

Powers of the eyepiece (10X) multiplied by objective lenses determine total magnification.

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Electron Microscopes

More powerful; some can magnify up to 1,000,000X

Use a magnetic field in a vacuum to bend beams of electrons

Images must be photographed or produced electronically

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Scanning Electron Microscope (SEM)

Electron microscope image of a spider

produces realistic 3D image

only the surface of specimen can be observed

Electron microscope image of a fly foot

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Transmission Electron Microscope (TEM)

produces 2D image of thinly sliced specimen

detailed cell parts (only inside a cell) can be observed

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