the longest objective (100x) combined with the ocular gives a total magnification of 1000X!
this objective is used to see bacteria and requires the oil immersion technique. If you take microbiology, or identify bacteria in your profession, you'll be using  this objective, but not in our class today. 

   as magnification increases, the area of the field of view decreases

FYI...if you ever take microbiology :)

using oil immersion lens
at 1000X total magnification

             how to use a light microscope

             low/scanning power
= 40X


medium power
= 100X


high power
​= 430X

     --->

 super important!!
always start your focus using the lowest magnification

   total magnification:

ocular magnification (10x)
​​X
​objective magnification

            as magnification increases, your light intensity decreases so you should open your iris to add light

the optical oil forms an interface between the slide and the objective,
reducing extraneous light and sharpening image

     total magnification