Ward's World Activity Guides

7. Compare your drawings and the physical models at each magnification. • Compare the level of detail visible at each magnification. • Compare an actual salt crystal to your clay models. Think about how much they increase in size and what this means about what can be viewed at each magnification. • Compare the fields of view. Think about how much they decrease in size and what this means about what can be viewed at each magnification. • In later activities, keep in mind that what you are viewing under the microscope is almost always 3-dimensional, just like the salt crystals. 8. Calculate the field of view when using each lens. • At 40X, the field of view of the digital microscope is approximately 4.5 mm. • The field of view is inversely proportional to the increase in magnification: 4.5 mm x 40 / ___ = ___ For example, the field of view at 100X is 4.5 mm x 40 / 100 = 1.8 mm. • Compare these calculated values to your measured diameters of the field of view. How closely do they match? 9. Return to 40X magnification and examine the salt crystals again, this time using the mini-digital screen that is on top of the digital microscope. • Using the transparent ruler, again measure the size of the salt crystal. (This is the same measurement you made earlier.) • Compare the level of detail you can see this way to what you see using the eyepieces. • This view is comparable to looking through the eyepieces, in terms of the magnification and the level of detail you can see (though sometimes the digital view isn't quite as crisp). • Take the transparent ruler, hold it in front of the mini-digital screen, and measure the size of the salt crystal image. How does the size of the salt crystal on the mini-screen compare to the size of a salt crystal? Is it 40X as large? 10. Examine and measure the salt crystals on your computer screen. • Using the software's measurement tool, again measure the size of the salt crystal. You are using a different tool, but the measurement is the same one you've made several times now. • Take the transparent ruler, hold it in front of the computer screen, and measure the size of the salt crystal image. How does the size of the salt crystal on the computer screen compare to the size of a salt crystal? Is it 40X as large? How does it compare to the size of the image on the mini-screen? Image size is distinct from level of magnification. • Under Tools, access the Magnifier option. • Observe your image of the salt crystals at 2X, 4X, 8X, and 16X magnification using this tool. Note: Despite the term used by the software, you haven't changed the microscope's level of magnification, just the size of the image. The image is larger, but you aren't getting additional details. 11. Examine and measure the salt crystals that are projected in front of the class, and discuss what you see in terms of the size of the crystal, the magnification of the crystal, and the size of the image. • Take a ruler or meter stick, hold it in front of the projection screen (trying to stay out of the way as much as possible), and measure the size of the salt crystal image. How does the size of the salt crystal on the screen compare to the size of a salt crystal? To the sizes of the salt crystal as viewed on the other screens? Again, image size is distinct from level of magnification. If you want to see additional details, you need to go to a higher level of magnification. Understanding Magnification and Scale (student activity sheet con't) + ward ' s science

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