C1.1 A window on a new world

INTRODUCTION

Have you used a microscope before? Microscopes help you see things that cannot be seen with the naked eye. A basic microscope consists of two lenses (an eyepiece and an objective lens) that can magnify an object several hundred times.

Read Pages 243-246

Turn to page 243 of the textbook and read the introductory paragraph of “A Window on a New World.” Continue by reading “Early Microscopes and Microscopists” and “Improvements in Lens Technology” on pages 243 and 244. You will gain knowledge about early microscopes and the people who built and/or used them.

learning activities

1. What ideas about scientific study did Aristotle provide the science community?

2. Who is credited with building the first microscope?

3. What are the three main components of a basic light microscope?

4. What did Robert Hooke discover about the structure of cork?

5. Why was van Leeuwenhoek able to produce single-lens microscopes that were better than the compound microscopes of his day?

Microscopes

Science 10 Biology requires you have a strong foundational knowledge of the microscope parts and functions. You most likely have already used a microscope in previous science courses and are probably familiar with the parts and use of a microscope. This section will allow you review the parts of a microscope and its functions.

Virtual Microscope

Use the link provided to further study the microscope virtually.

www.ncbionetwork.org/iet/microscope/

LEARNING ACTIVITIES

Refer to page 478 at the back of the textbook to answer the following questions:

Complete each statement by filling in the blanks with the correct parts of the microscope.

a. The lens at the upper end of the body tube is called the______________________.

b. The _____________________ objective lens should be used to locate a specimen on a slide.

c. The ______________________ should never be used with the high-power lens.

d. The ______________________ holds the three objective lenses.

e. The microscope should be carried by grasping the _________________ with one hand and holding the ___________________ with the other hand.

f. The ______________________ is used to focus the medium- and high-power lenses.

g. Another name for the eyepiece is _____________________.

CALCULATING MAGNIFICATION

Magnification

An increase in the apparent size of an object calculated as the product of the magnifying power of the objective lens and the magnifying power of the eyepiece.

LEARNING ACTIVITY

Turn to page 244 of the textbook and read “Skill Practice: Calculating Magnification.”
Answer questions a. and b. of “Skill Practice: Calculating Magnification.”

FIELD OF VIEW

The field of view is the area you see when you look through the eyepiece of a microscope. The diameter of the field of view using a low- or medium-power lens can be found by setting a transparent, plastic ruler on the stage of the microscope. The method is described in “Magnification and Field of View” on pages 478 and 479 of the textbook.

Note: The numbers shown in Figure 8.2 represent millimetres (mm), not centimetres.

You will not see any marks or numbers between or above the long lines representing millimetres when you view a transparent ruler under low power of a microscope. The marks and numbers were added to the diagram on page 479 of the textbook and in Figure C1.6 on page 245 so you can give the measurements for the exercises that follow to the nearest tenth of a millimetre.

This diagram is what you will normally see through a microscope lens when you view a transparent, plastic ruler under low power (40 X).

LEARNING ACTIVITIes

Study Example 8.1 on page 479 of the textbook.

a. What is the diameter of the field of view for the low-power lens in millimetres (mm) and in micrometres (μm)?

b. What is the diameter of the field of view for the medium-power lens in millimetres (mm) and in micrometres (μm)?

c. How is the diameter of the field of view in micrometres (μm) obtained for each lens power?

d. What happens to the diameter of the field of view as the magnification increases?

e. Calculate the field of view of a 100 X high-power lens.

2. Suppose you measure the low-power field of view with a ruler and it is 2 mm. The high-power magnification is 10 times the low-power magnification

a. What is the distance across the field of view under the high-power lens in millimetres (mm)?

b. What is the distance across the field of view under the high-power lens in micrometres (μm)?

c. If the specimen covers three-quarters of the field of view under the high-power lens, what is the length of the specimen in micrometres (μm)?

Once you have completed the required readings and learning activities for sections C1.1, you are now ready to complete the following labs:

Lab:

"C1- Microscope Lab and Investigation"
"C1- Basic Cell Structure and Investigation"

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