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The Microscope: A Window on a New World

Explore the history and advancements of microscopes and lenses, and learn how they have revolutionized our understanding of cells and the structure of living things. Discover how scientists like Robert Hooke and Antoni van Leeuwenhoek made groundbreaking observations using early microscopes, and develop your skills in microscopy, including magnification, field of view, scale, and estimating actual size.

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The Microscope: A Window on a New World

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  1. Science 10 – Unit CBIOLOGY Chapter 1 – The Microscope

  2. C1.1A window on a new world A section of human lung tissue affected by lung cancer.

  3. Early microscopes & lenses • a better understanding of cells and the structure of living things came hand-in-hand with the development of microscope technology • before the 1500s, scientists could only observe what they could see with the naked eye

  4. The average human can see objects no smaller than 0.1mm (or 10-4m). How small is that?

  5. Post-1500s • in the 1500s, the theory of optics and lenses was developed • these theories allowed scientists to invent tools that made more detailed observations possible

  6. The Janssen brothers • Hans & Zacharias Janssen invented the first microscope in 1595 • the brothers were Dutch eye-glass makers • considered to be a compound microscope because it used more than one lens

  7. Robert Hooke • in 1660, improved on the Janssens’ design by adding: • a third lens • a light to illuminate the objects

  8. Robert Hooke • used his microscope to observe living and non-living objects • made detailed drawings of his observations and published them in a book called Micrographia • Latin for “a record very small objects”

  9. Robert Hooke • Hooke observed a cross-section of cork, which he thought was non-living • observing that it was full of empty air chambers, he called these tiny chambers “cells” • these chambers turned out to be the remnants of living cells

  10. Antoni van Leeuwenhoek • working around the same time as Hooke • the first person to observe the movement of living single-celled organisms • Leeuwenhoek’s microscope only had a single lens – called a simple microscope • the lenses were of much higher quality, and allowed him to magnify objects up to 250X

  11. Skills in microscopy • Magnification: • how many times larger the image is compared to the original • magnification = (power of the objective lens) x (power of the eyepiece) • eyepiece lens – always 10X • objective lens • low power: 4X • medium power: 10X • high power: 40X

  12. Magnification – practice problems • What is the magnification of a microscope with a 10X ocular (eyepiece) lens, and a 10X objective lens? • magnification = (10X)(10X) = 100X • How much more powerful is the magnification on high power compared to low power? • magnification high = (10X)(40X) = 400X • magnification low = (10X)(4X) = 40X • the high powered magnification is 10 times more powerful

  13. Field of view • the area that can be seen through the microscope with a particular objective lens • field of view can be described in terms of field diametre or field area • when the lens power increases, field of view decreases

  14. Field of view • the field diameter on low power can be measured by placing a ruler under the microscope • the field diameter on high power can be calculated using this formula: high-power field diameter = low-power magnification low-power field diameter high-power magnification

  15. Field of view – practice problems • The image to the right is the view through low power. What is the field diameter of this microscope? • 29 mm • What is the field diameter on high power? • 2.9mm • How many times smaller is the field diameter on high power as on low power? • one tenth

  16. Scale • a comparison between the size of a drawing and the actual size of the object • to calculate it, compare the diameter of the circle in the drawing with the diameter of the field of view you calculated previously • e.g. a drawing with a diameter of 90mm done from low power would roughly have a scale of 90mm:29mm or 3:1.

  17. Actual size • once you know the field diameter, you can estimate an object’s size by noting how much of the field of view it occupies • this can be done by estimating how many times across the object would fit • e.g. if it would fit 10 times across, it takes up 1/10th of the field of view • e.g. if the field of view is 29mm and a cell takes up about 1/3 of the field of view, it’s actual size is about 10mm

  18. Actual size – practice problem • our field of view on high power was found to be 2.9mm. What is the actual size of this cell, as viewed under high power? • (2.9mm)(1/2)=1.45mm • what is its size in micrometers? (hint: 1 mm = 1000 µm) • 1.45mm = 1450 µm

  19. Homework: • Skills practice p. 244 a & b • Check and Reflect p. 246 #1, 3, 4, 8

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