Microscope Lab

Mrs. Orwar’s sure fire way to find an image every time! 1.Start on low power (red objective) 2.Place your slide centered over the light hole or aperture (opening) 3.With the coarse adjustment, move the lens and slide as close together as they will go 4.Look through the ocular and slowly use your coarse adjustment upward until you find the image Write these in your notes

5.Focus with fine adjustment and make sure the specimen in centered 6.Without touching anything else!!!- Move to medium power 7.Focus again and center 8.Without touching anything else!!!- move to high power

9.The lens may look like it is going to touch the slide, but if done properly it should not!! 10.DO NOT USE YOUR COARSE ADJUSTMENT FOR ANY REASON ON HIGH POWER!!!!!!!

11.With your fine adjustment…Focus by turning it a little bit towards you or a little bit away from you 12.Adjust your light if necessary 13.If you cannot find your specimen, go back to low power and repeat steps from there

Supplies for Lab  Microscope (obviously)  250 mL Beaker  Eyedropper  Slide  Coverslip  Clear Ruler (with mm)  Newspaper  Scissors  Potato  Iodine  Hair/thread  Salt  Sugar

Follow the steps given for each of the procedures to follow  At some point you will see a “water bubble”  They are exciting to look at and usually have a dark thick ring around them with light inside.  You should know how to identify one.  I will sign your paper when you show me one!

How to prepare a "wet mount" of the letter "e"  Cut out the letter “e” from the newspaper supplied.  Place it on the middle of the slide and add a drop of water using the eyedropper.  Place a coverslip over the specimen at a 45 degree angle and drop it so to prevent air bubbles.

Inversion  On a piece of paper, title this section “The Letter E”.  Draw the letter "e" as it appears on the slide (NOT through the microscope).  Then draw the letter "e" as it appears looking through the microscope on scanning power, low power and high power.  Label each picture with the magnification used.

Water Bubble  Don’t forget to locate one on this slide OR the next and stop me when I pass by for a signature.

Answer on paper  While looking through the microscope, move the slide slowly to the right. In what direction does the letter "e" move?  Now move the letter up. In what direction does it move?  What does “inversion” mean?

Starch grains and the field of view.  Prepare a wet mount of starch grains by first cutting a piece of potato.  Then using a single edged razor blade, gently scrape the surface (not the skin). Place the whitish liquid from the blade on a slide.  Add a drop of iodine stain to the solution and place a cover slip over it.  Examine the specimen under low power. The blue ovals are starch grains.

 Label this section of your paper “Starch Grains”.  Count the number of starch grains on low power (If there are too many to conveniently count, sample them) Diagram what you see on your paper; include the magnification.  Now without moving the slide, switch to high power and count the grains in the field of view. Diagram what you see on your paper; include the magnification.

Answer on paper  Explain why the number of grains you counted in the low power field of view is different than the number you counted in the high power field of view.  What is meant by the field of view?

Water Bubble  Don’t forget to locate one on this slide or the next and stop me when I pass by for a signature.

Depth of focus  Make a wet mount using a light hair strand and a dark hair strand from your classmates. ASK BEFORE TAKING!  You can also use a dark and light thread.  Lay the dark hair/thread over the blonde hair/thread in an “X”.  Using the low power, find the point at which the hairs or threads cross.

Water Bubble  Don’t forget to locate one on this slide or the next and stop me when I pass by for a signature.

Answer on paper  Label this section “Hair/Threads”.  What happens when you slowly focus up and down?  What do you predict will be the effect on the depth of focus when you use a higher power of magnification?  What relationship exists between higher powers of magnification and the depth of focus?

Diameter of the Field  Place a clear plastic ruler across the stage so the inner edge of the ruler is visible as a vertical line along the diameter of the low power field. Be sure you are looking at the millimeter side of the ruler.  Label this section “Ruler” on your paper.  Estimate the number of millimeters, that you see along the field and note this on your paper.

 Convert the millimeter measurement value into micrometers. 1 mm = 1000 micrometers (µm).  You have now calculated the diameter of the low power field.

Dry mounts  A dry mount is exactly as it sounds: the thing you plan to observe is placed on the slide with a cover slip over it. No water is needed. This kind of mount is usually used for inanimate objects or things that do not need water to live.

 Label this section “Sugar and Salt”.  Prepare 2 dry mounts- one of sugar and one of salt  Draw them on low power and then a single grain on high power  Remember to label your drawings with the magnification.

Clean Up  Make sure your work area is clean  Put your slides and coverslips back  Wrap your cord properly  Return your microscope  Turn in your drawings and questions