Title: Magnification

1. Title: Magnification Lesson Objectives: 1. Can I calculate magnification, image size and actual size of a cell? Grade C-A Starter: Recap quiz….

2. Recap quiz… • What is the difference between a micrometer and micrometre? • How many micrometres in a millimetre? • What is the unit after micrometre? • How many micrometres in a nanometre? • Calculate the calibration: X4 objective lens and a x10 eyepiece (=) Micrometer is 1mm long with 100 divisions (what is each division worth?)

3. Magnification Photomicrographs often have magnification bars to allow calculation of the actual size of specimens. 4.55μm

4. I – Image size A – Actual size M – Magnification Remember: I AM The Magic Triangle…. I ÷ x A M

5. Magnification In this exercise you will calculate the magnification and/or true size of the following: 1 2 3 4 5 8 6 7 10 9

6. Before we begin: • Note: • Numbers written like this: 1.26 x 105 mean you move the decimal point to the right. In this case you move it 5 times: • 1.26 x 105 = 126000.0 1.260000 .

7. Before we begin: • Note: • Numbers written like this: 1.26 x 10-5 mean you move the decimal point to the left. In this case you move it 5 times: • 1.26 x 10-5 = 0.0000126 0.00001.2 6

8. Have a go at these: 14500.0 • 1.45 x 104 = • 0.37 x 107 = • 86.41 x 10-3 = • 2.65 x 10-2 = 3700000.0 0.08641 0.0265

9. Figure 5.1 Paramecium caudatum x600

10. Figure 5.1 Paramecium caudatum Measured length = 142mm 142 ÷ 600 = 0.237mm 0.237mm = 237μm x600

11. Figure 5.2 chloroplasts x9000

12. Figure 5.2 chloroplasts Mean measured length of the four largest chloroplasts = 39.25mm 39.25 ÷ 9000 = 0.0044mm 0.0044mm = 4.4μm x9000

13. Figure 5.3 a bacterium Measured length = 128mm 128 ÷ 0.002mm = magnification Magnification = x64000

14. Figure 5.4 seven week human embryo

15. Figure 5.4 seven week human embryo Measure the actual length of the scale bar and divide by the length it represents Magnification = 25 ÷ 10 = x2.5

16. Figure 5.5 head of a fruit fly

17. Figure 5.5 head of a fruit fly Measure the actual length of the scale bar and divide by the length it represents Magnification = 12.5 ÷ 0.2 = x62.5

18. Figure 5.6 pollen grain

19. Figure 5.6 pollen grain (a) Measure the actual length of the scale bar and divide by the length it represents Magnification = 25 ÷ 0.02 = x1250 (b) 47mm (c) 47 ÷ 1250 = 0.0376mm 0.0376mm = 37.6μm

20. Figure 5.7 red blood cells in an arteriole

21. Figure 5.7 red blood cells in an arteriole Measured length of scale bar = 30mm Magnification = 30 ÷ 0.01 = x3000 Diameter = 25mm [approx] Actual diameter = 25 ÷ 3000 = 0.0083mm 0.0083mm = 8.3μm

22. Figure 5.8 a mitochondrion

23. Figure 5.8 a mitochondrion Measured length of scale bar = 30mm Magnification = 30 ÷ 0.002 = x15000 Measured width = 34mm Actual width = 34 ÷ 15000 = 0.0023mm 0.0023mm = 2.3μm

24. Figure 5.9 bacteriophage [a type of virus]

25. Figure 5.9 bacteriophage [a type of virus] Measured length of phage = 29mm Magnification = 29 ÷ 0.0002 = 145000 Magnification = 1.45 x 105

26. Figure 5.10 potato cells starch grains

27. Figure 5.10 potato cells Mean diameter of the cells = 38mm [approx] Measured length of scale bar = 24mm Magnification = 24 ÷ 0.1 = x240 Diameter of the cells = 38 ÷ 240 = 0.158mm 0.158mm = 158μm

28. Magnification…. • The resolving power of the unaided eye is approximately 0.1mm • The maximum useful magnification of light microscope is around x1500 • Plant and animal cells typically measure around 20µm • Many organelles are as small as 25nm – beyond the resolving power of the light microscope [wavelength of light is 500nm approx] • Wavelength of electron beam is 0.005nm • Maximum resolving power of the electron microscope is 0.2nm

29. Question 11….