LIGHT MICROSCOPE Care of Microscope Carry the microscope

LIGHT MICROSCOPE

Care of Microscope Ø Carry the microscope holding the arm and support the base with your other hand Ø Never touch lenses with your fingers Ø Never lower course adjustment knob when looking through the eyepiece lens Ø Always focus first with low power Ø Do not use course adjustment knob with high power objective lens in place Ø Stored to microscope covered

CELLS VARY IN SIZE Bacteria is approximately 0. 5 to 2. 0 μm Sciatic nerve cell (nerve running down your leg from sciatic region of your back to your toes) can be as large as 1 meter Ø Diameter of an RBC = 7. 5μm Ø Ø

Magnification Ø enlargement of an image brought about by lenses (multiply eyepiece by objective)

Calculating Total Magnification Eyepiece x multiplied by objective lens x Eyepiece Ø Scanning Ø Low Ø High Ø Oil = 10 x = 4 x = 10 x = 43 x = 97 x = 100 x Total magnification Ø 10 x 4 = 40 Ø 10 x 10 = 100 Ø 10 x 40 = 400 or Ø 10 x 43 = 430 Ø 10 x 97 = 970 or Ø 10 x 100 = 1000 Ø

Focusing Microscope Clean the microscope with lens tissue 2 Start on the shortest objective lens 3 Turn light down and center slide over light 4 Bring objective lens and slide together until they stop 5 Use coarse adjustment knob with low power objective lens to locate object 6 Turn to high power objective lens refocus with fine adjustment knob 7 Adjust light using diaphragm at each step as needed 1

Estimate the size of a cell Ø Light microscope measurements are in micrometers/microns (μm). Ø There are 1, 000 μm in one millimeter, or mm.

Estimate the size of an object The low power field of view is about 4500 μm Ø How many stars would it take to cover the diameter of the field of view? Ø Seven stars would do it. Ø Divide seven into 4500 μm Ø The star is about 630 μm Ø an answer between 560 + 640 μm is reasonable Ø

Estimate the size of an object Ø The low power field of view is about 1700 μm How many wood chips would it take to cover the diameter of the field of view? Ø Four chips. Ø Divide four into 1700 μm Ø Ø The chip is about 425 μm

2. Electron microscope Ø Uses a stream of electrons instead of light to see images which are magnified more than with a light microscope.