How to use a microscope and oil immersion

Summary

This video tutorial guides students through the process of using a microscope for microbiological analysis, focusing on oil immersion techniques for accurate bacterial identification. It emphasizes the importance of proper focus, correct slide placement, and careful oil immersion to prevent microscope damage. The tutorial provides practical tips for troubleshooting, such as adjusting the condenser and ensuring the slide is correctly oriented. Students are reminded to be patient and methodical, as mastering the microscope is crucial for success in microbiology. The video concludes with proper microscope storage instructions to ensure equipment longevity.

Takeaways

• 😀 Make sure to review how to use a microscope before class, especially if it's been a while since you've used one.
• 😀 Oil immersion is essential for viewing bacteria under the microscope; you must use it to ensure clarity and accuracy of the specimen.
• 😀 It’s critical to focus on the specimen first with the 10x objective lens before moving to higher magnifications.
• 😀 The condenser must be adjusted correctly before starting, ensuring it’s in the right position to focus properly.
• 😀 Avoid frustration with oil immersion—if you don’t succeed the first time, keep trying and focus on using the technique correctly.
• 😀 Always check your slide placement to avoid upside-down slides, which can cause focusing issues.
• 😀 The only lens that should ever have oil on it is the 100x objective lens. Never apply oil to the 10x or 40x lenses.
• 😀 If you can't find the specimen under the oil immersion lens, go back to the 10x and start over to re-focus.
• 😀 Never use coarse adjustment when focusing under the 100x lens—only fine adjustment should be used.
• 😀 After finishing with the microscope, clean the 100x lens with lens paper, dabbing gently—not rubbing, to remove oil.

Q & A

What is the main focus of the video script?

The main focus of the video script is to guide students through the process of using a microscope in microbiology, specifically when working with bacterial stains and oil immersion.

Why is it important to know how to use a microscope before coming to class?

It is important to know how to use a microscope before coming to class to save time and avoid frustration. The instructor won't have time to teach basic microscope usage during the class, and students need to focus on finding bacteria quickly during the practical session.

What should students do if they struggle with oil immersion during the lab?

Students should not be alarmed if they struggle with oil immersion at first. They will be required to use oil immersion, but if they have difficulty, they should keep practicing and not give up. The instructor will assist with oil immersion techniques.

How should the condenser be adjusted for optimal focusing?

To adjust the condenser for optimal focusing, students should use a loop over the light source, focus on it through the microscope, and then adjust the condenser until the loop comes into focus. This ensures better focusing of the specimen.

What is the correct order for adjusting magnification when using the microscope?

Students should start with the 10x objective to find the specimen. Then, they should move to the 40x objective using only the fine adjustment knob, and finally, move to the 100x oil immersion objective. The slide should not be moved during these steps.

Why is oil immersion necessary at 100x magnification?

Oil immersion is necessary at 100x magnification to reduce light refraction, which allows for a clearer view of the specimen and accurate color differentiation (e.g., distinguishing between pink and purple bacteria in a Gram stain).

What should students avoid doing with the 40x and 10x lenses?

Students should avoid putting oil on the 40x and 10x lenses, as oil can permanently damage these lenses. Only the 100x lens should ever have oil on it.

What is the correct technique for applying oil to the slide?

The oil should be applied with a dropper or a small medicine dropper to the slide, ensuring the smallest drop possible. Students should not touch the slide with the dropper and must carefully place the oil directly on the slide.

What should be done if a student cannot find the specimen under the 100x lens?

If the specimen is not visible under the 100x lens, students should go back to the 10x objective, refocus, and then attempt to refocus on the 40x before returning to the 100x. They should never move directly from the 100x to the 40x lens to avoid getting oil on the 40x lens.

How should the microscope be cleaned after use?

To clean the microscope, students should gently dab the oil off the 100x lens with lens paper, avoiding rubbing. They should also remove the slide and properly dispose of it after checking with lab partners if it's useful for sharing.