1. a) In order to sharpen the objective with a 40x objective (400x total magnification), the objective must be closer to the sample than with a 10x objective (100x total magnification), so the sample is out of focus.
b) At 400x total magnification, the field of view is narrower than at 100x total magnification.
c) A 40x objective (i.e. 400x total magnification) has a higher numerical aperture than a 10x objective (i.e. 100x total magnification) and therefore provides better resolution.
d) Shallow depth of field.
e) The amount of light is reduced.
f) Shorter working distance.
2. The best objective for observing bacteria is the 100x objective, which is the immersion objective.
3. Without the addition of immersion oil, the sample will look blurry and will not give maximum resolution.
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