Using a Microscope Question Student Name Date Can a microscope be used to estimate the size of small objects?

Hypothesis If you can estimate the number of objects that could fit across a microscope’s field of view, then you can estimate the size of the object.

Materials Compound mic. • Clear ruler Slide with “e”

Procedures 1. The diameter of the field of view at low power, (40X) is ______________ (include the units, eg. mm). 5 mm 2. The diameter of the field of view at medium power, (100X) is ______________ (include the units, eg. mm). 2 mm 3. The ratio of high power to low power is: 400/40 = _________. 10 4. The field of view at high power, therefore, is 1/10th of low power, or 5/10 = 0.5 mm

Procedures cont’d Use the prepared slides of the letter e. Place it on the stage right side up. Use low power. 5. The number of “e’s” that could fit across the field of view at low power is ____________. 6. How does the “e” appear when you look through the eyepiece? _______________________________________ 7. Try moving the slide to your right. Which way does the “e” appear to move when viewed through the eyepiece? ____ 8. Try moving the slide up. Which way does the “e” appear to move? __________________ 9. Why is there a difference? _______________________

Procedures cont’d 5. Use the prepared slides of the letter e. Place it on the stage right side up. Use low power. 6. The number of “e’s” that fit across the field of view at low power is ____________. 3 7. How does the “e” appear when you look through the eyepiece? _______________________________________ Larger, upside down 8. Try moving the slide to your right. Which way does the “e” appear to move when viewed through the eyepiece? ____ left 9. Try moving the slide up. Which way does the “e” appear to move? __________________ down 10. Why is there a difference? _______________________ The lenses invert the images.

Analysis p. 9 Record your answers to a,b,e, and f (p. 9), using full sentences and indicating the question in your answer.

Analysis p. 9 a. The coarse-adjustment know should not be used with the higher powered lenses because… ____________________ It may lift the stage into the lenses, cracking them. b. As you move from low to high magnification… _______ The diameter of the field of view gets smaller/decreases. e. For scanning several objects, …____________________ a low power would be better because it gives a larger field of view. f. The cell can’t be seen when you move to higher power because…______________ i) It is no longer in the field of view. ii) A solution is to first centre the cell in the field of view before going to higher power.

Conclusion Was your Hypothesis supported, ie. Can you estimate the size of small objects if you know the field of view? How? Count the number of the objects you can see across the field of view. Divide this number into the field of view, to find the actual size of the small object. Eg: if the F.O.V is 5 mm, and you can see 3 “e’s”, then the size = 5/3, which = 1.7 mm