bis_104_midterm_exam_i_key2_fall_07 - Page 2

bis_104_midterm_exam_i_key2_fall_07 - Page 2 - Will this...

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PART I 1. In the equation: d = (0.61) ( ) / N.A., what exactly does “d” represent? (2) d = resolution = the minimal distance of separation between two points in a specimen that can be seen as two distinct entities. 2. In the above equation, N.A. stands for “numerical aperture”. What exactly is the numerical aperture? (2) N.A. is derived from (n) x (sin ), where n = refractive index of the medium between the specimen and the objective lens and represents the amount of light from the specimen that is captured by the objective lens. N.A. is an inherent property of individual objective lenses. 3. In your haste to view an interesting specimen on your microscope, you forget to put a drop of immersion oil on the cover slip prior to using your 63x oil immersion objective lens.
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Unformatted text preview: Will this omission affect the magnification of your specimen? Will it affect the resolution of your specimen? Why or why not? (2) Magnification will not be affected, but resolution will be improved and optimized by using the appropriate immersion oil. That is, the value of (n) x (sin ) = N.A. will increase. 4. What specific feature of electron microscopy (EM) provides for increased magnification and resolution compared to light microscopy? (2) In electron microscopy high energy, short wavelength electrons are used to create an image, whereas in light microscopy. The longer wavelengths of visible light photons limits the resolution and the effective magnification. Demo...
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