Objec&ve: Today we will Sta&ons to learn how to use our microscopes (parts, magnifica&on, depth of field, preparing a wet mount, crea&ng scien&fic drawings) Honors: Addi&onal sta&on about measuring under a microscope (micrometer) Debrief So that we can Iden&fy the parts of a microscope & their func&ons Focus the microscope under low & high magnifica&on Calculate total magnifica&on. Prepare slides Create scien&fic drawings Honors: Iden&fy the size of the field of view and measure the size of objects at different magnifica&ons
Bell Work: Brainstorm: What s the smallest thing that can be seen with current microscope technology? Please raise your hand when you have your idea!
Today: Prac&ce our microscope skills so that we can look at cells during Unit 2!
Keep Our Scopes Safe! Follow the Rules for CFC!
Microscope Technique Carrying:
Microscope Technique Cleaning:
Microscope Technique Focusing: Use the coarse focus knob on low powers (4x and 10x) On high powers (40x and 100x), use the fine focus knob ONLY.
Here s why!
Let s Try Focusing Together: 1) Check your microscope to make sure that it is on the lowest power objec&ve (4x, red). 2) Hold the slide by the label and place it on the stage. Be sure that it is flat and secured. 3) Use the stage adjustment knob to center the slide under the objec&ve lens. 4) While looking through the ocular lens, turn the coarse focus knob un&l the specimen comes into view. 5) Use the stage adjustment knob to center the specimen. Then, twist the turret to change to the 10x (yellow) objec&ve. Adjust focus if needed, first with the coarse focus, then with the fine focus knobs. 6) Twist again to the 40x (blue) objec&ve. Adjust focus using the FINE focus knob only.
You should see...
Sta&ons: Each sta&on will guide you through learning about the microscopes. Please answer all ques&ons on your lab sheet as you work. These are your notes for this topic, so make sure you are thorough! You will be turning this in as well.
Debrief: The e Slide
Magnifica&on in Light Microscopes: Most light microscopes have 2 sets of lenses: Ocular lenses At the eye piece Usually 10x Objec&ve lenses Above the stage Our microscopes have 4 objec&ves: 4x, 10x, 40x, and 100x To calculate total magnifica&on: MULTIPLY the magnifica&ons of each lens!!!
Did you also no&ce
How a Light Microscope Works: Light Source Shines through the specimen Diaphragm Controls the amount of light that passes through Lenses Magnify the image
How a Light Microscope Works: Why do images appear upside down?
Debrief: The Crossed Thread Slide
The thickness of the plane (layer) of focus. Depth of Field:
Pollen Grains Under a Light Microscope:
Pollen Grains Under an Electron Microscope:
Scien&fic Drawing:
Debrief: The Micrometer Slide
This tenth of a millimeter is divided into 10 parts. Each part is 10 micrometers.
Micrometers: 1 m = 1,000 mm 1mm = 1,000 µm
Measure Our Field of View: 4x Objective (40x Magnification)
Es&mate the Size of Specimens: If this specimen is viewed at 40x, what is its approximate size?
Closing: A B
None J Homework:
Sta&on 1: Parts of the Microscope 1) Each slip of paper describes a part of the microscope. Please read about the part and then locate it on the microscope. Try carefully adjus&ng these parts to see what they do! 2) Record the names of these parts on your notes sheet by labeling the microscope photo. 3) Quiz each other to see if you can use the correct names and locate the parts!
OCULAR LENS Lens that is in the eyepiece. OBJECTIVE LENSES Lenses that are located just above the stage. (Our microscopes have 4 objec&ve lenses so that we can view specimens at different magnifica&ons.) OIL IMMERSION LENSE The highest power objec&ve lens. To use this lens, you must place a drop of a special oil on the slide. Otherwise, it will not focus. COARSE FOCUS Knob that moves the stage up and down to bring the image into focus. FINE FOCUS Knob that makes small adjustments to sharpen the focus of your image. STAGE Flat surface that holds the slide.
STAGE CONTROL Knob that moves the stage in all 4 direc&ons (lel, right, forward & backward) so that you can view different parts of the slide. SLIDE CLIP Metal arm that holds slide in place for viewing LIGHT SOURCE Bulb that provides light below slide LIGHT CONTROL Dial that adjusts the intensity of the light POWER SWITCH Switch that turns the light on/off ARM Structural part of the microscope that connects the eyepiece, objec&ves, stage & base. BASE - Structural founda&on of the microscope.
Sta&on 2: Video - How to Make a Wet Mount Slide Please watch the video at: hops://www.youtube.com/watch? v=qssme_oxv-0 Stop the video aler 8:30 minutes. Record the procedure for making a wet mount slide on your lab sheet.
Sta&on 3: Make a Slide Use your instruc&ons from sta&on two to prepare TWO slides. 1) For your first slide, please use the pond water as your specimen. 2) For your second slide, please use a small amount (just a few threads!) of cooon. View your slides under the microscope using the two lowest power objec&ve lenses (4x and 10x).
Look for Wee Animalcules in Your Pond Water Slide Fun fact: Anton Van Leeuwenhoek was a scien&st from the Mid-1600 s. He helped to develop early microscopes. He used his microscopes to look at pond water. When he saw living singled-celled organisms, he called them wee animalcules!
Sta&on 3: Clean Up Please take your slide apart by removing the cover slip. Wipe both the cover slip and slide with a Kimwipe. (You may rinse it in the sink if needed.) Coverslips are very fragile. Be gentle! J Please let me know if any coverslips break so that I can dispose of them properly.
Sta&on 4: The Leoer e This sta&on will help us understand how using different lenses affect the magnifica&on of what we see. Please view the prepared slide of the leoer e under the 3 lowest objec&ves (4x, 10x and 40x) and record your observa&ons on your notes sheet. Calculate the magnifica&on of each image.
Calcula&ng Total Magnifica&on: The ocular lens (the lens you look through in the eyepiece) makes the image appear 10 &mes larger than it actually is. So, we say it has a magnifica&on of 10x. The objec&ve lenses (the 4 lenses above the stage) also magnify the image, either by 4x, 10x, 40x, or 100x. To get your TOTAL MAGNIFICATION, mul&ply the powers of each lens you are using. (For example, if my ocular is 10x and I am using the 4x objec&ve, then my TOTAL MAGNIFICATION is 40x.)
Sta&on 5: Crossed Threads Please view the slide using first the 4x and then the 10x objec&ve lenses ONLY. Your task is to figure out which thread is on top. You should no&ce that as you focus the image, different threads will come into focus at different &mes. (Hint: The one that comes into focus first is on top!)
Depth of Field Even though the specimen on this slide appears thin enough to be two-dimensional, it DOES have thickness. Magnifica&on emphasizes the thickness of the specimen. Therefore, you see different levels of the specimen come into clear focus as you adjust the focus. The beoer a microscope is, the more layers it will be able to show in focus at one &me. This is called the microscope s depth of field.
Sta&on 6: Scien&fic Drawing Drawing for science is different than drawing ar&s&cally. In science, we are trying to capture our observakons about important structures in our specimen. It does not maoer if our drawing is preoy, only that it is accurate. Discuss: Compare the scien&fic and ar&s&c drawings on the next page. What differences do you see between them?
Example: Scien&fic Drawing vs Ar&s&c Drawing
Characteris&cs of a Good Scien&fic Drawing: Title Total magnifica&on Label important structures Draw within a circle (to show the total field of view) Draw with clear lines (no sketching/shading) Is an ACCURATE representa&on of what you see Use color, if your specimen has color Honors: Also include at least 1 measurement of size
Discuss: What characteris&cs of a good scien&fic drawing do you see here?
Prac&ce: View the salt crystals slide using the 10x (yellow) objec&ve. Use your notes and the checklist below to create a good scien&fic drawing of what you see. Note: Your drawing should not look like anyone else s drawing because it should show YOUR observa&ons of the slide that YOU focused. J
Sta&on 7 (Honors): Measurement Please answer ques&on #1 on your notes sheet first to beoer understand what micrometers are. Then, use the slide micrometer to measure the diameter of the field of view. (See #2.) Finally, use your new knowledge to answer #3 on your notes sheet!
Sta&on 7 (Honors): Measurement We typically measure microscopic specimens in units of micrometers (or microns ). A micrometer (μm) is 1/1000 of a millimeter (mm) -- so micrometers and millimeters are related in the same way that millimeters and meters are. A slide micrometer is basically an ioy-bioy ruler that we can use to measure our specimens while viewing them. The smallest marks on our slide micrometer are 10 μm.
This tenth of a millimeter is divided into 10 parts. Each part is 10 micrometers.