Overview
This lecture introduces the basics of microscopy, focusing on the parts and use of light microscopes, the meaning of object, image, magnification, and resolution.
Parts of a Light Microscope
- The base supports the entire microscope.
- The arm connects the base to the top section.
- The light source is usually a lamp or mirror to reflect room light.
- The stage holds the microscope slide with the sample.
- Objective lenses (typically three) offer different magnifications (e.g., 10x, 20x, 50x).
- Eyepiece lens at the top provides further magnification for viewing.
- The body tube connects the eyepiece to the lenses.
- Coarse and fine focusing knobs adjust the image to bring it into focus.
Key Microscopy Terms: Object & Image
- The object is the actual sample (e.g., onion cells) on the slide.
- The image is what you see when you look through the eyepiece.
How Light Microscopes Work
- Light is reflected from the source (mirror or lamp) up through the sample on the stage.
- The light then passes through an objective lens, the eyepiece lens, and finally to the eye.
- Lenses spread the light rays so the image appears much larger than the object.
Magnification
- Magnification is how many times larger the image is compared to the object.
- Formula: Magnification = Image Size ÷ Object Size.
- Magnification shows size increase, not necessarily detail.
Resolution
- Resolution is the shortest distance between two points that can still be seen as separate.
- Higher resolution means greater detail and a less blurry image.
- Images can have the same magnification but differ in resolution and clarity.
Key Terms & Definitions
- Object — the real sample you are examining.
- Image — the enlarged version of the object seen through the microscope.
- Magnification — the ratio of image size to object size.
- Resolution — the minimum distance at which two points can be distinguished as separate.
Action Items / Next Steps
- Practice microscopy questions as suggested in the linked resources.