T1- Microscopy

Resolution

Resolution

• how well a microscope distinguishes between two points that are close together

• a higher resolution means that the image can be seen more clearly and in more detail

Light microscopes

• pass light through the specimen

• let us see things like nuclei and chloroplasts

• can be used to study living cells

Electron microscopes

• use electrons rather than light

• have higher magnification and resolution than light microscopes

• let us see much smaller things in more detail, like the internal structure of mitochondria and chloroplasts

• cannot be used to view living cells

How to view a specimens using a light microscope?

1. Take a thin slice of the specimen

2. Use a clean slide and put one drop of water in the middle of it using a pipette. Use tweezers to place specimen on slide

3. Add a drop of stain if specimens is completely transparent/colourless

4. Place a coverslip at one end of the specimen, holding it at an angle with a mounted needle, and carefully lower it on the slide

5. Press down gently so no air bubbles are trapped under it. Then clip the slide onto the stage

6. Select the lowest-powered objective lens

7. Use the coarse adjustment knob to move the stage up so that the slide is just underneath the objective lens. Then, looking down the eyepiece, move the stage downwards until the specimen is nearly in focus

8. Then adjust the focus with the fine adjustment knob, until you get a clear image. Position a clear ruler on the stage and use it to measure the diameter of the circular area visible (your FOV)

9. If you need to see your specimens with greater magnification, swap to a higher - powered objective lens, refocus and recalculate your FOV accordingly.

Components of a microscope

• eyepiece lens

• coarse adjustment knob

• fine adjustment knob

• high and low power objective lenses

• clip

• stage

• lamp

Formula for total magnification (when you know the power of lenses used)

total magnification = eyepiece lens magnification x objective lens magnification

Formula for magnification (when you don’t know which lenses were used)

magnification = image size/real size

Millimetre (mm) in standard form

x 10^-3

Micrometer (µm) in standard form

x 10^-6

Nanometre (nm) in standard form

x10^-9

Picometre (pm) in standard form

x 10^-12