Presentation on theme: "Compound Light Microscope. TOTAL MAGNIFICATION Power of the eyepiece (10X) multiplied by objective lenses determines total magnification."— Presentation transcript:
Compound Light Microscope
TOTAL MAGNIFICATION Power of the eyepiece (10X) multiplied by objective lenses determines total magnification.
Magnification ObjectiveOcular Eyepiece Total Magnification Low Power4 x10 x40 x Medium Power 10 x 100 x High Power40 x10 x400 x
Field of View Field of View (FV) is the illuminated circle that you see when looking through the ocular eyepiece. If we know the diameter of the FV then we can estimate the size of our microorganisms.
Field of View With our microscopes the diameter of the FV under low power is 4 mm FV is measured in micrometers or microns. 1 mm = 1000 microns Therefore, our FV under low power is 4000 microns
Using the Field of View to Estimate Microscopic Measurements If an organism takes up ½ of the FV under low power, it must be about 2000 microns in length
Making cheek cell and onion cells slides Cheek – Scrape the inside of your cheek with a toothpick – Rub toothpick onto the slide and add a drop of methylene blue – Place a cover slip onto the slide. Observe Onion – Peel off inner epidermis of onion using forceps – Place on slide – Put a drop of iodine and a cover slip onto your slide – Observe
How does the FV change as Magnification goes Up?? As magnification goes up, the size of the FV gets smaller. If magnification increases 2x, the FV is divided by 2x, or 2x smaller. If we switch from low power (4X) to medium power (10X), the increase in magnification is 2.5 times (10X/4X). The FV under medium power will be 1600 microns (4000/2.5)
Calculating the Diameter of the Field of View Step 1 Calculate the Increase in Magnification. New Objective Old Objective Step 2 Divide the old F of V by the increase in magnification calculated in Step 1 Old F of V (Microns) Increase in Mag
To Calculate the Changing FV Low – 5x; Med – 10x; High – 50x Low FV = 5mm (1000um x 5mm= 5000um) Step 1 – Calculate the increase in Magnification Ex – 10x/5x = 2 Step 2 – Calculate the reduction of the FV 5000um/2 = 2500um