- Using the oil immersion lens. To examine bacteria and other very small objects, we will need to use the oil immersion (100X lens). Special techniques must be used when using the 100X objective. With the 10-fold increase in magnification provided by the ocular lens, we are approaching the theoretical limit of light microscopy so must obtain the best possible resolution in order to get a clear image the sample.
- Because when we use the powerful lens, light will refract with different refractive index and it will make the quality of the image decrease. So, we put oil on the top of the coverslip to eliminate it. (Light will not go to the air when the lens is touching the oil and, it always stay in liquid and the bending will reduce.)