The Microscope

• The basic unit of structure is the cell.
• Cells are often described as the building blocks of life.
• Every cell arises from pre-existing cells.
• Cells are tiny structures measured in micrometres (µm). They can only be viewed under a microscope.

1. The Compound Light Microscope (can only view the nucleus)

2. The Electron Microscope (to view cell ultrastructures)

1. The Compound Light Microscope

Eyepiece Lens	Magnifies the object.
Coarse Focus Wheel	For rough focusing.
Fine Focus Wheel	Brings the specimen into clear focus.
Stage Clips	To hold the slide.
Nosepiece	Revolves to move the desired lens into place.
Objective Lens	Magnifies the image.
Stage	Holds the slide.
Diaphragm	Controls the amount of light passing through the specimen.
Mirror/Light Source	Reflect light through the stage, allowing the specimen to be seen more clearly.

Magnification

To calculate the total magnification, multiply the magnification of the eyepiece lens by the magnification of the objective lens.

Eyepiece lens	Objective lens	Total magnification
x10	x4	x40
x15	x10	x150

2. Electron Microscope

An electron microscope allows the cell ultrastructure to be seen (the cell organelle).

1. Transmission Electron Microscope (TEM): Sends a beam of electrons through a thin specimen to reveal the internal structure in great detail.
2. Scanning Electron Microscope: Sends a beam of electrons over the surface of the specimen to view its outer structure.