The Light Microscope

1. The Light Microscope

2. The light microscope Eyepiece lens Nosepiece Objective lens Stage and Stage Clips Coarse adjustment knob Condenser Diaphragm Fine adjustment knob Light Source Base

3. Parts of the microscope Magnifies the specimen Used to focus on Low Power Used to focus on Medium and High Power Magnifies the specimen Allows the objective lens to be changed Holds the slide in place on the stage Controls amount of light entering condenser Concentrates light into a beam Projects light upwards through microscope

4. Total Magnification • Microscopes have an eyepiece lens and several objective lenses. • These objective lenses are normally referred to as Low, Medium and High Power. Total Magnification = Eyepiece Lens x Objective Lens Example: Eyepiece Lens (x10) Objective Lens (x4) Total Magnification = (x10) x (x4) = x40

5. Total Magnification x100 x10 x16 x16 x640 x16

6. Field of View • The field of view is the area of the slide which can be seen when looking down through the microscope. • The low power objective lens is ALWAYS used first because this allows a larger area of the slide to be seen. • This then allows you to choose which part of the specimen on the slide you want to view in further detail at higher magnifications. • Before increasing magnification the area you have chosen should be moved to the centre of the field of view. (N.B. The following slides demonstrate this.)

7. Low power • Using the low power objective lens and the coarse adjustment knob allows the word “BIOLOGY” to be seen clearly. • If we wanted to look at the letters “BIO” more closely then the slide has to be moved so that these letters are centre of the field of view. BIOLOGY BIOLO

8. Medium power BIO • Using the medium power objective lens and the fine adjustment knob allows the letters “BIO” to be seen clearly. • If we wanted to look at the letter “B” more closely then the slide has to be moved so that this letter is centre of the field of view.

9. High power • Using the high power objective lens and the fine adjustment knob allows part of the letter “B” to be seen in more detail.

10. Cells • All living organisms are made of cells. • Cells are the building blocks of life itself. • Unicellular organisms: consist of ONE cell. e.g. amoeba • Multicellular organisms: consist of two or more cells. e.g. earthworm

11. Animal Cells • Nucleus • Controls ALL of the cells activities • Cytoplasm • Site of all of the chemical reactions • Cell Membrane • Controls the entry and exit of materials

12. Plant Cells • Nucleus • Cytoplasm • Cell Membrane • Cell Wall • Made of cellulose, provides support. • Chloroplast • Contains chlorophyll, essential for photosynthesis • Sap vacuole • Contains solution of sugars and salts

13. Slide Preparation and Staining • The material should be very thin to allow light to pass through it. Some types of material can be smeared onto the glass. 2. Most cell material istransparentand needs to be stainedwith one or more coloured dyes. This makes different parts of the cell stand out and easier to see. 3. The material should be covered with a coverslipto stop it drying out. The coverslip should be lowered with a mounted needle. This helps to prevent too many air bubbles being trapped in the preparation. Stains Examples of coloured dyes or stains which can be used to stain cells are: a) Iodine stainb) Methylene Blue stain

14. Onion cells under the microscope – low power

15. Onion cells under the microscope – medium power

16. Onion cells under the microscope – high power

17. Magnified even further

18. Measurement • Cells are so small that they cannot be measured in millimetres ! • They are measured in micrometers(µm) • There are 1000 micrometers in a millimeter. 1mm = 1000 µm

19. Converting to micrometers • Convert the following measurements from mm into µm (Show your working) • 2 mm • 0.5 mm • 0.04 mm • 1.06 mm • 0.072 mm • 0.123 mm • 0.88 mm • 0.022 mm

20. Converting to micrometers • 2 mm x 1000 =2000 µm • 0.5 mm x 1000 = 500 µm • 0.04 mm x 1000 = 40 µm • 1.06 mm x 1000 = 1060 µm • 0.072 mm x 1000 = 72 µm • 0.123 mm x 1000 = 123 µm • 0.88 mm x 1000 = 880 µm • 0.022 mm x 1000 = 22 µm

21. Converting to millimeters • Convert the following measurements from µm into mm (Show your working) • 3000 µm • 250 µm • 86 µm • 900 µm • 47 µm • 505 µm • 1050 µm • 636 µm

22. Converting to millimeters • 3000 µm 1000 = 3mm • 250 µm 1000 = 0.25 mm • 86 µm 1000 = 0.086 mm • 900 µm 1000 = 0.9 mm • 47 µm 1000 = 0.047 mm • 505 µm 1000 = 0.505 mm • 1050 µm 1000 = 1.05 mm • 636 µm 1000 = 0.636 mm

23. Estimating Cell Size 160 cm Can you estimate the size of the frog?

24. Estimating Cell Size To estimate the size of a cell you need to know: • The diameter of the field of view • The number of cells which fit across the diameter of the field of view

25. Can you estimate the size of the cell? Estimating Cell Size 0.9 mm

26. Estimating Cell Size Diameter of the Field of View Estimate of cell size = Number of cells that fit across 900µm = 6 150 µm = The estimated size of the cell is 150 µm.