Microscope Basics

Parts and focusing

Label the Compound Light Microscope

Ocular lens

Body TubeCoarse Adjustment KnobFine adjustment KnobRevolving nosepieceObjective lenses (4x, 10x, 40x)ArmStage Stage ClipsDiaphramLight source

Base

Focusing with a Microscope Plug in and turn on. Lower stage completely. Turn nosepiece to low objective. Raise stage with coarse objective until specimen is seen. (Big

knob) Fine focus the specimen. Centre specimen in the field of view. Rotate nosepiece to medium power objective. Refocus with fine adjustment. Re-centre the specimen. Refocus with fine adjustment (be careful not to break the

slide) Adjust the condenser(Light) Start over to look at another specimen. Carrying and storage instructions.

Robert Hooke In 1665, the English physicist Robert Hooke

looked at a sliver of cork through a microscope lens and noticed some "pores" or "cells" in it.

Hooke was the first person to use the word "cell" to identify microscopic structures when he was describing cork.

What he actually observed was the cell walls of the once living plant cell.

Historic Microscope - link

Early Microscopes - Anton Van Leeuwenhoek The father of microscopy, Anton Van

Leeuwenhoek of Holland (1632-1723). Anton Van Leeuwenhoek was the first to see and

describe living blood cells, bacteria (1674), yeast plants and single-celled organisms.

Robert Brown In 1820, scientist Robert Brown

observed and recorded the first instance of a tiny sphere inside a plant cell called the nucleus.

Shortly after the nucleus was found inside animal cells as well.

The discovery of these cells and their nucleus provided the foundation of cell theory: all living things are composed of one or more cells and the cell is the most basic unit of life.

Big and Small Link – Scale of the Universe

Compound Light Microscopes Uses light to illuminate objects Has two lenses Magnification limited to 2000x (400x at LHHS)

Transmission Electron Microscope(TEM) Uses beams of electrons and can magnify subjects

up to 2 000 000X Has two limitations:

Good only for thin specimens Only dead cells can be observed

Scanning Electron Microscope

Electrons are reflected from the surface of the specimen

Produces a 3-D image Good for the thicker specimens Lacks the magnification and resolution of the

transmission electron microscope

Pollen

Dust Mite

Magnification Magnification = Objective lens X Ocular lens

(4x, 10x, 40x) (10x)

Calculating the size of a specimen

Calculating the size of a specimen – ex. Med viewObject size = Size of field of View

Number of objects across field of view

Object size = 1.72 mm 14

Object size = 0.1 mm