OL1 – 02 - MICROSCOPES

THE MICROSCOPE (UD2) The microscope allowed humans to see a whole new world of life. Our limited senses did not allow us to see this microscopic life previously. The Janssen brothers made the first known microscope in 1590. Robert Hooke made the microscope more famous by making the compound microscope. Finally Anton von Leeuwenhoek was able to improve the microscope with his ability to create specific glass lenses. His improvements allowed him to see microscopic organisms closer and more clearly.

With the invention of the microscope, it has revealed a whole new world to scientists. They were able to extend the limits of what could be seen. The microscope made it possible to make observations, ask questions, and find answers like never before.

Types of Microscopes All biologists have used a microscope to better understand the living world. Microscope provides an enlarged image of an object. Different Types of Microscopes 1) The Light Microscope (LM) 2) Scanning Electron Microscope (SEM) 3) Transmission Electron Microscope (TEM)

Light Microscopes Light microscopes can magnify specimens up to 1500 times their actual size. The specimen must be thin and often dyed. Offers only a 2D type of image. stoma

Electron Microscopes Uses beams of electrons instead of light. Clearly magnify specimens more than 100,000 times their actual size. Used to study parts of cells or even individual proteins. Cannot be used to study living organisms because the specimen must be in a vacuum. Images are colorized with computers to see details easier.

Scanning Electron Microscope (SEM) stoma Scans the surface of a specimen. The specimens outer surface is coated with a thin layer of metal which deflects the electrons back to a computer that will form a 3D image.

Transmission Electron Microscope (TEM) Transmits electrons through a thin slice of a specimen. The TEM makes a 2D images similar to that of a light microscope but at a much higher magnification. stoma

STEPS FOR USING THE MICROSCOPE When carrying the microscope, use 2 HANDS. Turn the low power objective lens in to line with the light. When it is in proper position, it will click. Open the diaphragm as wide open as possible. Now look through the eyepiece. The round circle of light is called the field of view. If the lenses are dusty, use a piece of lens paper to wipe the ocular lens and the tips of each of the objective lenses. Wipe in one direction only! Place the slide of whatever you are looking at on the stage. Now, using the course adjustment knob on the side of the microscope, bring the object into focus. If you need more magnification, place your object in the middle of your field of view and rotate your objective lenses to get the medium power objective lens. Now when you focus only use the fine adjustment knob to make your object clearer. If you still need higher magnification, repeat step 7 and use the high power objective lens. When you are finished using the microscope: Remove the slide and put it back into the proper case Make sure the lowest objective lens is in place and the stage is lowered. Wrap cord around the arm Turn the body tube towards the arm

STEPS FOR MICROSCOPE DRAWINGS All diagrams must be done in pencil, on 8 ½ x 11 white unlined paper. Draw on one side of the paper only. Diagrams need to be large, no more than 2 per page. Be sure diagrams are dark enough to be seen easily (use a sharp pencil)

All diagrams must have a title All diagrams must have a title. The title should be printed above the diagram, and include the name of the object, type of slide, whether stained or unstained, eg. Cross section, wet mount, unstained, etc…. Genus and species names need to be underlined Homo sapiens blood smear

Name, Period and Date in upper right hand corner. Draw the field of view for all microscope diagrams, and make sure you draw a perfect circle for the field of view. Draw a circle slight to the left of the center of the page. Use a template to draw your circle – a beaker or petri dish.

Your diagram will not be a “drawing” – use no shading, sketching, stippling, or cross – hatching. Keep diagrams simple and precise. Artistic ability does not count, but neatness does! If there are many similar objects in your field of view, you need only draw a few of them. For a large object with a lot of detail, draw individual cells for a section, then simply outline the tissues for the rest.

Label lines must be horizontal, parallel, and drawn with a ruler Label lines must be horizontal, parallel, and drawn with a ruler. They should never cross. Labels are on the right side of your drawing and should line up vertically. Be sure label lines touch object. Arrows are not necessary. Labelling should be printed and in lower case letters ONLY. Magnification, including formula, needs to be included with each diagram. Your calculations should be on the bottom of the page.

Calculations for MICROSCOPE DRAWINGS Total Magnification: The Magnification Used 1. Find out what objective lens you are using and their magnification - (low Power, medium power or high power) 2.Find out the magnification of the eyepiece. 3.Use the following formula to find the Total Magnification.   Total Magnification = Ocular Lens x Objective Lens = ________ X

Example: Human Cheek Cell – Medium Power

Diameter of Field of View Actual Size: How big is it? 1. Find out the field of view (Use the following charts to determine the diameter of the field of view. 2. Estimate how many times your specimen will fit across the field of view. 3. Calculate the actual size of your specimen using the following formula. Objective Lens Diameter of Field of View Low Power 3.5 mm (millimeters) 3500 um (micrometers) Medium Power 1.4 mm 1400 um High Power 0.35 mm 350 um   Actual Size = Diameter of Field of View = _____________um Number of Specimens that fit across

Magnification of Drawing: How big your drawing is to its actual size 1. Measure the size (width or length) of YOUR drawing in mm. 2. Convert the size of the drawing from mm to um (1mm = 1000 um) 3. Calculate the magnification of your drawing using the following formula:   Magnification of Drawing = size of drawing = X Actual Size

Microscope Drawing & Calculations Take a slide of frog blood or onion root slide Go through the steps to get it to high power. Pick three to four cells to draw. Label the following: Cell Membrane / Cell Wall Nucleus Cytoplasm Complete ALL microscope drawing calculations.

Example Take a slide of frog blood. Go through the steps to get it to high power. This should be what you see … Draw the field of view (a circle). Pick three to four cells to draw.

http://virtualurchin.stanford.edu/microscope.htm

Let us review …. What is wrong with the following lab drawing?