For each calculation, you need to know the wavelength of light being used and NA (numerical aperture) of the objective lens.

For each calculation, you need to know the wavelength of light being used and NA (numerical aperture) of the objective lens.  Use the information provided in bold below but NOTE, some information needed to answer the questions is only provided in the lab manual.

You have a microscope equipped with the following:

– a yellow filter and a blue filter.  With the yellow filter in place, only yellow light can pass through.  The blue filter allows only light of wavelength 0.45 um (450nm) to pass through.

– a 40x dry objective with an NA of 0.7

– a 100x dry objective with an NA of 0.9

– a 100x oil objective with an NA of 1.3

What is the resolving power when the following objective lenses and filters are in place?

 1. 40X dry objective used with the blue filter gives an r.p. of

2.100X dry objective used with the yellow filter gives an r.p. of

3.100X dry objective used with the blue filter gives an r.p. of

4.100X oil objective used with the blue filter gives an r.p. of

5. The combination that gives the best resolution is 6. If you were using the blue filter and  100X oil lens combination, would you be able to see a structure that was 10um in diameter (hint: resolving power indicates the smallest thing you can see clearly, anything larger is also clearly visible)?

2. Answer these questions about cultivation technique:

a) Why are media and cultures in Petri plates stored upside down?

b) Why is it necessary to heat a loop to redness before using it to transfer bacteria?

c) Why is it necessary to cool a loop after it has been sterilized before placing it into a bacterial culture?

3.Answer these questions about making smears for staining:

a) What are three qualities of an effective and useful bacterial smear?

b) What would happen to the smear if you failed to “heat fix” the slide before staining?

c) Review the lab manual Where are Microbes and list below all the environments you will sample.  For those where you have some options, list environments you would be curious to sample.

d) Are you expecting the same result on all 8 environment sample plates.  Why or why not – explain your answer for full credit.

 

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