* Immersion oil: The 100x objective is designed for use with immersion oil. This oil has the same refractive index as glass, which allows light to pass through the objective without being refracted. This results in a clearer image. Without a coverslip, the oil will come into contact with the slide, which can damage the objective lens and the specimen.
* Sample distortion: A coverslip helps to flatten the specimen and provide a consistent distance between the objective and the sample. Without a coverslip, the specimen may be uneven, leading to distortion and blurry images.
* Air bubbles: Air bubbles trapped between the objective and the specimen can also cause distortion. A coverslip helps to eliminate these bubbles.
* Contamination: The lack of a coverslip can make the specimen more susceptible to contamination from the environment.
* Objective damage: Using a 100x objective without immersion oil can scratch or damage the lens.
However:
* Some techniques exist for viewing specimens without coverslips: These techniques involve using special mounting media that have a similar refractive index to water, which eliminates the need for oil immersion. These techniques are usually reserved for very thin specimens or situations where a coverslip is not practical.
* Certain specimens can be viewed without coverslips: For example, very small specimens or those that are already mounted on a slide may not require a coverslip.
In most cases, it is best to use a coverslip with a 100x objective to ensure clear, high-quality images and protect both the objective and the specimen.
