Microscopes Biology 11

The History 4 Many people experimented with making microscopes 4 Was the microscope originally made by accident? (Most people were creating telescopes) 4 The first microscope was 6 feet long!!! 4 The Greeks & Romans used “lenses” to magnify objects over 1000 years ago.

The History 4 Hans and Zacharias Janssen of Holland in the 1590’s created the “first” compound microscope Zacharias Jansen

The History 4 Anthony van Leeuwenhoek and Robert Hooke made improvements by working on improving the lenses Anthony van Leeuwenhoek Robert Hooke Hooke Microscope

How a Microscope Works Convex Lenses are curved glass used to make microscopes (and glasses etc.) Convex lenses bend light and focus it in one spot.

How a Microscope Works Ocular Lens (Magnifies Image) Objective Lens (Gathers Light, Magnifies And Focuses Image Inside Body Tube) Body Tube (Image Focuses) Bending Light: The objective (bottom) convex lens magnifies and focuses (bends) the image inside the body tube and the ocular convex (top) lens of a microscope magnifies it (again).

The Parts of a Microscope:

Body Tube Nose Piece Objective Lenses Stage Clips Diaphragm Light Source Ocular Lens Arm Stage Coarse AdjCoarse Adjustment Fine Adjustment Base

Body Tube 4 The body tube holds the objective lenses and the ocular lens the proper distance apart Diagram

Nose Piece 4 The Nose Piece holds the objective lenses and can be turned to choose a different magnification objective. Diagram

Objective Lenses 4 The Objective Lenses increase magnification (usually from 4x to 40x) Diagram

Stage Clips 4 These 2 clips hold the slide/specimen in place on the stage. Diagram

Diaphragm 4 The Diaphragm controls the amount of light on the slide/specimen Turn to let more light in or to make dimmer. Diagram

Light Source 4 Projects light upwards through the diaphragm, the specimen and the lenses 4 Some have lights, others have mirrors where you must move the mirror to reflect light Diagram

Ocular Lens/Eyepiece 4 Magnifies the specimen image Diagram

Arm 4 Used to support the microscope when carried. Holds the body tube, nose piece and objective lenses Diagram

Stage 4 Supports the slide/specimen Diagram

Coarse Adjustment Knob 4 Moves the stage up and down (quickly) for focusing your image, use only with low power objective lens! Diagram

Fine Adjustment Knob 4 This knob moves the stage SLIGHTLY to sharpen the image Diagram

Base 4 Supports the microscope Diagram

Label the microscope diagram 4 Page 627 in the textbook will help

Parts of a microscope

What the parts do 1) the lens you look through, magnifies the specimen 2) supports the microscope 3) holds objective lenses 4) magnify the specimen (2) 5) supports upper parts of the microscope, used to carry microscope 6) used to focus when using the high power objective 7) where the slide is placed 8) regulates the amount of light reaching the object 9) used to focus when using the low power objective 10) provides light 11) hold slide in place on the stage

Caring for a Microscope 4 Carry it with 2 HANDS…one on the arm and the other on the base. 4 Make sure it’s on a flat surface, away from the edge of the desk. 4 Don’t pull on the cord to unplug it. 4 Clean lenses only with lens tissue.

Carry a Microscope Correctly

Using a Microscope 4 Start on the lowest magnification, with the stage lowered. 4 Place slide on stage and lock with clips. 4 Use coarse adjustment knob to center the sample and focus on the object. 4 Adjust light source using the diaphragm. 4 Use fine adjustment to focus.

Using a Microscope (cont’d) 4 Rotate the nosepiece to increase magnification from lowest to highest. 4 Use only the fine adjustment knob to focus on high power.

Microscopy – involves 2 processes 1. Magnification 4– enlargement 2. Resolution (resolving power) 4- sharpness of the image

Magnification 4 The ability to increase the size of the image of a specimen. 4 Total magnification of an image is found by multiplying the power of the ocular lens by the power of the objective. 4 The larger the magnification the less area you are able to see.

Resolution 4 The ability to see details clearly. 4 in order for the increased magnification of a microscope to be of use, its resolution must also be increased 4 resolution is dependant on the quality of the lens and is limited when using light microscopes

Microscope video. 4 Fill out response while you watch.

Simple Microscope 4 Anton van Leewenhoek was the first to use the single lens microscope for biological purposes. 4 Consisted of a single lens 4 used today for quick observations in the field 4 specimens may be alive for examination. 4 but it has low magnification

Compound Light Microscope 4 Consists of two lenses, the ocular and the objective, both of which magnify the image 4 these two lenses form the optical system. 4 Structural parts that hold the specimen and the lenses is called the mechanical system

Compound Light Microscope 4 Uses: –good for basic lab work (up to 1500x) –can be used to view living things but most specimens are dead –usually used with stain 4 Disadvantages: –cannot view cell structures –low resolution

Stereo microscope (dissection) 4 Two sets of lenses- an ocular and an objective for each eye 4 Uses –allows the scientist to view images as 3-D –used to study external structures and for dissections –specimens may be kept alive for examination. 4 Disadvantage –Low magnification (6-50x)

Phase Contrast (lens) Microscope 4 Changes the way light passes through a living specimen with phase plates 4 Can see cell structures that are not usually visible under a compound microscope. 4 Useful for examining live specimens 4 But has a low magnification Frits (Frederik) Zernike won the Nobel prize 1953 for the development of this microscope.

Transmission Electron Microscope 4 Electron beam is sent through a vacuum chamber then electromagnets focus the image on a screen 4 an image can be magnified a million times so you can see cell structures and specimens smaller than a cell 4 Vacuum is needed, specimens are dead and required complex procedures to prepare them Also know as the TEM

Scanning Electron Microscope 4 Like the TEM, this microscope uses electrons to focus an image and is able to view things much smaller than the light microscope. 4 Unlike the TEM, the SEM allows the viewing of 3D images and has better resolution. 4 Vacuum is needed, specimens are dead and required complex procedures to prepare them. Lower magnification possible Also known as the SEM

Scanning electron micrograph (SEM) of various Pollen. Public domain image reference: Dartmouth Electron Microscope Facility, Dartmouth College

Microscope Calculations: